f = open("file_a_100000", "r")
a = f.readlines()

f = open("file_b_100000", "r")
b = f.readlines()

d = {}
for x in a:
    d[x] = 0

for x in b:
    if d.has_key(x):
        d.pop(x)
a = d.keys()

f = open("file_c_100000", "w")
for x in a:
    f.write(x + "\n")