#!/usr/bin/env python

import sys

if len(sys.argv) != 3:
    print("Usage: ",sys.argv[0], "filename mod-number")
    quit()

filename = sys.argv[1]
M = int(sys.argv[2])
i = 0
f = open(filename)
line = f.readline().rstrip()
while line:
    if (i % M) == 0:
        print(i,"行目:",line)
    i += 1
    line = f.readline().rstrip()

f.close()