import os
import sys

sought = sys.argv[1]
replace = sys.argv[2]
source = sys.argv[3]

f = open(source, "w")

while True:
    line = f.readline()
    resultFind = line.find(sought)

    if not resultFind == -1:
        resultFind += len(sought) - 1
        line = replace + line[resultFind : 0]
        f.writelines(line)
        print("ok")

f.close()