#!/usr/bin/python
# Python 2 and 3 compatible.

import sys, fileinput

if len(sys.argv) != 3:
    sys.stdout = sys.stderr
    print("difference <file1> <file2>")
    print('')
    print("Report lines in <file1> not present in <file2>.")
    sys.exit(1)

veto = set()
for line in fileinput.input(sys.argv[2]):
    veto.add(line)

for line in fileinput.input(sys.argv[1]):
    if line not in veto:
        sys.stdout.write(line)