import difflib

REPLACE='replace'
DELETE='delete'
INSERT='insert'
EQUAL='equal'

def unidiff(f1, f2, ctx):
    sys.stdout.write("--- %s\n" % (f1,))
    sys.stdout.write("+++ %s\n" % (f2,))

    c1 = open(f1).readlines()
    c2 = open(f2).readlines()

    m = difflib.SequenceMatcher(None, c1, c2)
    ops = m.get_opcodes()

    i = 0
    while i < len(ops):
	while i < len(ops) and ops[i][0] == EQUAL:
	    i=i+1
	if i == len(ops): break

	j = i
	st1 = max(0, ops[j][1]-ctx)
	st2 = max(0, ops[j][3]-ctx)
	while i < len(ops) and (ops[i][0]!=EQUAL or ops[i][2]-ops[i][1]<2*ctx):
	    i=i+1
	en1 = min(len(c1), ops[i-1][2]+ctx)
	en2 = min(len(c2), ops[i-1][4]+ctx)

	sys.stdout.write("@@ -%d,%d +%d,%d @@\n"
		    % (st1+1, en1-st1, st2+1, en2-st2))
	
	for k in range(st1, ops[j][1]):
	    sys.stdout.write(" %s" % c1[k])

	for (opcode, i1, i2, j1, j2) in ops[j:i]:
	    if opcode == EQUAL:
		for l in range(i1, i2):
		    sys.stdout.write(" %s" % c1[l])
	    if opcode == DELETE or opcode==REPLACE:
		for l in range(i1, i2):
		    sys.stdout.write("-%s" % c1[l])
	    if opcode == INSERT or opcode==REPLACE:
		for l in range(j1, j2):
		    sys.stdout.write("+%s" % c2[l])

	for k in range(ops[i-1][2], en1):
	    sys.stdout.write(" %s" % c1[k])

def __main__(args):
    unidiff(args[0], args[1], 3)

if __name__ == '__main__':
    import sys
    __main__(sys.argv[1:])