#!/usr/bin/env python3
import sys
def input():
    return sys.stdin.readline()[:-1]

def main():
    N, K = map(int, input().split())

    ball = N - K
    if K == 1:
        ball = 0
    print(ball)

if __name__ == '__main__':
    main() import sys sys def input():
    return sys.stdin.readline()[:-1] input return sys.stdin.readline()[:-1] sys.stdin.readline()[:-1] sys.stdin.readline() sys.stdin.readline sys.stdin sys stdin readline :-1 -1 def main():
    N, K = map(int, input().split())

    ball = N - K
    if K == 1:
        ball = 0
    print(ball) main N, K = map(int, input().split()) N map(int, input().split()) map int input().split() ().split () input split K ball = N - K ball N - K N K if K == 1:
        ball = 0
     K == 1 K 1 ball = 0 ball 0 print(ball) print ball if __name__ == '__main__':
    main() __name__ == '__main__' __name__ '__main__' main() main def input():
    return sys.stdin.readline()[:-1] def input():
    return sys.stdin.readline()[:-1] input def main():
    N, K = map(int, input().split())

    ball = N - K
    if K == 1:
        ball = 0
    print(ball) def main():
    N, K = map(int, input().split())

    ball = N - K
    if K == 1:
        ball = 0
    print(ball) main
#!/usr/bin/env python3
import sys
def input():
    return sys.stdin.readline()[:-1]

def main():
    N, K = map(int, input().split())

    ball = N - K
    if K == 1:
        ball = 0
    print(ball)

if __name__ == '__main__':
    main()
