import sys, math
from collections import deque

def input():
    return sys.stdin.readline()[:-1]

def mi():
    return map(int, input().split())

def ii():
    return int(input())

def i2(n):
    tmp = [list(mi()) for i in range(n)]
    return [list(i) for i in zip(*tmp)]

def main():
    N, K = mi()
    N -= K
    print(N if K!=1 else 0)

if __name__ == '__main__':
    main() import sys, math sys math from collections import deque 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 mi():
    return map(int, input().split()) mi return map(int, input().split()) map(int, input().split()) map int input().split() ().split () input split def ii():
    return int(input()) ii return int(input()) int(input()) int input() input def i2(n):
    tmp = [list(mi()) for i in range(n)]
    return [list(i) for i in zip(*tmp)] i2 list(mi()) for i in range(n) for i in range(n) i range(n) range n for i in range(n) list(mi()) list mi() mi tmp = [list(mi()) for i in range(n)] tmp [list(mi()) for i in range(n)] list(i) for i in zip(*tmp) for i in zip(*tmp) i zip(*tmp) zip *tmp tmp for i in zip(*tmp) list(i) list i return [list(i) for i in zip(*tmp)] [list(i) for i in zip(*tmp)] n n def main():
    N, K = mi()
    N -= K
    print(N if K!=1 else 0) main N, K = mi() N mi() mi K N -= K N K print(N if K!=1 else 0) print N if K!=1 else 0 K!=1 K 1 N 0 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 = mi()
    N -= K
    print(N if K!=1 else 0) def main():
    N, K = mi()
    N -= K
    print(N if K!=1 else 0) main def i2(n):
    tmp = [list(mi()) for i in range(n)]
    return [list(i) for i in zip(*tmp)] def i2(n):
    tmp = [list(mi()) for i in range(n)]
    return [list(i) for i in zip(*tmp)] i2 def ii():
    return int(input()) def ii():
    return int(input()) ii def mi():
    return map(int, input().split()) def mi():
    return map(int, input().split()) mi
import sys, math
from collections import deque

def input():
    return sys.stdin.readline()[:-1]

def mi():
    return map(int, input().split())

def ii():
    return int(input())

def i2(n):
    tmp = [list(mi()) for i in range(n)]
    return [list(i) for i in zip(*tmp)]

def main():
    N, K = mi()
    N -= K
    print(N if K!=1 else 0)

if __name__ == '__main__':
    main()
