f = open("file_a_1000", "r")
a = f.readlines()

f = open("file_b_1000", "r")
b = f.readlines()

i = 0
for x in b:
    if a.count(x) > 0:
        a.remove(x)

f = open("file_c_1000", "w")
for x in a:
    f.write(x + "\n")