208 lines
7.8 KiB
Python
208 lines
7.8 KiB
Python
#!/usr/bin/env python3
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"""
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Recursive ext4 directory dumper by inode number.
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Bypasses all metadata validation - uses extent trees directly.
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"""
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import struct, os, sys, stat
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from pathlib import Path
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DEV = '/dev/dm-0'
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BLOCK = 4096
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BACKUP_SB_BLOCK = 32768
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# ── low-level helpers ────────────────────────────────────────────────────────
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def read_at(f, offset, size):
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f.seek(offset)
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return f.read(size)
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def parse_superblock(data):
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sb = {}
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sb['inodes_count'] = struct.unpack_from('<I', data, 0)[0]
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sb['blocks_count'] = struct.unpack_from('<I', data, 4)[0]
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sb['blocks_per_group'] = struct.unpack_from('<I', data, 32)[0]
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sb['inodes_per_group'] = struct.unpack_from('<I', data, 40)[0]
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sb['inode_size'] = struct.unpack_from('<H', data, 88)[0]
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sb['magic'] = struct.unpack_from('<H', data, 56)[0]
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sb['desc_size'] = struct.unpack_from('<H', data, 254)[0] or 32
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return sb
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def parse_gdt_entry(gdt_data, offset, desc_size):
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lo = struct.unpack_from('<I', gdt_data, offset + 8)[0]
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if desc_size >= 64:
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hi = struct.unpack_from('<I', gdt_data, offset + 40)[0]
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return lo | (hi << 32)
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return lo
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def parse_extent_tree(data, inode_offset):
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base = inode_offset + 40
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magic, entries, _, depth = struct.unpack_from('<HHHH', data, base)
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if magic != 0xF30A:
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return []
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extents = []
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if depth == 0:
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for i in range(min(entries, 4)):
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o = base + 12 + i * 12
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if o + 12 > len(data): break
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l_block = struct.unpack_from('<I', data, o )[0]
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ee_len = struct.unpack_from('<H', data, o + 4)[0]
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start_hi = struct.unpack_from('<H', data, o + 6)[0]
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start_lo = struct.unpack_from('<I', data, o + 8)[0]
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phys = (start_hi << 32) | start_lo
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if phys > 0:
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extents.append((l_block, phys, ee_len & 0x7FFF))
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else:
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# Depth > 0: extent index node - follow first child
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# (handles large dirs gracefully)
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o = base + 12
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ei_leaf_lo = struct.unpack_from('<I', data, o + 4)[0]
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ei_leaf_hi = struct.unpack_from('<H', data, o + 8)[0]
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extents.append((0, (ei_leaf_hi << 32) | ei_leaf_lo, 1))
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return extents
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def read_inode(f, sb, gdt_data, inum):
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"""Return raw inode block data and offset within it."""
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grp = (inum - 1) // sb['inodes_per_group']
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local_idx = (inum - 1) % sb['inodes_per_group']
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tbl_block = parse_gdt_entry(gdt_data, grp * sb['desc_size'], sb['desc_size'])
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byte_off = local_idx * sb['inode_size']
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blk_off = byte_off // BLOCK
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slot = byte_off % BLOCK
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data = read_at(f, (tbl_block + blk_off) * BLOCK, BLOCK)
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return data, slot
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def read_dir_entries(f, sb, gdt_data, inum):
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"""Return dict of name -> (child_inum, ftype)."""
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idata, slot = read_inode(f, sb, gdt_data, inum)
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entries = {}
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for _, phys, length in parse_extent_tree(idata, slot):
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for blk in range(length):
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try:
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bdata = read_at(f, (phys + blk) * BLOCK, BLOCK)
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offset = 0
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while offset < BLOCK - 8:
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e_ino, rec_len, name_len, ftype = \
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struct.unpack_from('<IHBB', bdata, offset)
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if rec_len < 8 or offset + rec_len > BLOCK:
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break
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if e_ino != 0 and name_len > 0:
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name = bdata[offset+8:offset+8+name_len]\
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.decode('utf-8', errors='replace')
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entries[name] = (e_ino, ftype)
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offset += rec_len
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except OSError:
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pass
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return entries
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def dump_file(f, sb, gdt_data, inum, dest_path):
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"""Extract a regular file by inode to dest_path."""
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try:
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idata, slot = read_inode(f, sb, gdt_data, inum)
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size_lo = struct.unpack_from('<I', idata, slot + 4)[0]
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size_hi = struct.unpack_from('<I', idata, slot + 108)[0]
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size = size_lo | (size_hi << 32)
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extents = parse_extent_tree(idata, slot)
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# Check for inline data (EXT4_INLINE_DATA_FL = 0x10000000)
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flags = struct.unpack_from('<I', idata, slot + 32)[0]
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if flags & 0x10000000:
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# Data stored in inode body - skip for now
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return False
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written = 0
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with open(dest_path, 'wb') as out:
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for _, phys, length in sorted(extents):
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for blk in range(length):
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if written >= size:
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break
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chunk = read_at(f, (phys + blk) * BLOCK, BLOCK)
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remaining = size - written
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out.write(chunk[:remaining] if remaining < BLOCK else chunk)
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written += min(BLOCK, remaining)
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return True
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except OSError:
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return False
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def dump_symlink(f, sb, gdt_data, inum, dest_path):
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"""Extract symlink target."""
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try:
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idata, slot = read_inode(f, sb, gdt_data, inum)
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size = struct.unpack_from('<I', idata, slot + 4)[0]
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if size <= 60:
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# Fast symlink - target in inode block area
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target = idata[slot+40:slot+40+size].decode('utf-8', errors='replace')
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else:
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extents = parse_extent_tree(idata, slot)
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if not extents:
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return False
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bdata = read_at(f, extents[0][1] * BLOCK, BLOCK)
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target = bdata[:size].decode('utf-8', errors='replace')
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os.symlink(target, dest_path)
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return True
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except (OSError, IndexError):
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return False
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# ── recursive dumper ─────────────────────────────────────────────────────────
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FTYPE_REG = 1
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FTYPE_DIR = 2
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FTYPE_SYM = 7
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def dump_tree(f, sb, gdt_data, inum, dest_dir, depth=0, visited=None):
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if visited is None:
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visited = set()
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if inum in visited:
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return
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visited.add(inum)
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try:
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entries = read_dir_entries(f, sb, gdt_data, inum)
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except Exception:
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return
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os.makedirs(dest_dir, exist_ok=True)
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for name, (child_inum, ftype) in entries.items():
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if name in ('.', '..'):
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continue
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# Sanitise name
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safe_name = name.replace('/', '_').replace('\x00', '')
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dest = os.path.join(dest_dir, safe_name)
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try:
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if ftype == FTYPE_DIR:
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dump_tree(f, sb, gdt_data, child_inum, dest, depth+1, visited)
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elif ftype == FTYPE_REG:
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dump_file(f, sb, gdt_data, child_inum, dest)
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elif ftype == FTYPE_SYM:
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dump_symlink(f, sb, gdt_data, child_inum, dest)
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except Exception as e:
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print(f" WARN: {dest}: {e}", file=sys.stderr)
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# ── main ─────────────────────────────────────────────────────────────────────
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def main():
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if len(sys.argv) < 3:
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print(f"Usage: {sys.argv[0]} <inode> <dest_dir>")
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sys.exit(1)
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root_inum = int(sys.argv[1])
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dest_dir = sys.argv[2]
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with open(DEV, 'rb') as f:
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sb_data = read_at(f, BACKUP_SB_BLOCK * BLOCK, 1024)
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sb = parse_superblock(sb_data)
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assert sb['magic'] == 0xef53
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num_groups = (sb['blocks_count'] + sb['blocks_per_group'] - 1) \
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// sb['blocks_per_group']
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gdt_data = read_at(f, (BACKUP_SB_BLOCK + 1) * BLOCK,
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num_groups * sb['desc_size'])
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print(f"Dumping inode {root_inum} -> {dest_dir}")
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dump_tree(f, sb, gdt_data, root_inum, dest_dir)
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print("Done")
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if __name__ == '__main__':
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main()
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