def main():
    n, k = map(int, input().split())
    if k == 1:
        print(0)
    else:
        print(n-k)


if __name__ == '__main__':
    main() def main():
    n, k = map(int, input().split())
    if k == 1:
        print(0)
    else:
        print(n-k) main n, k = map(int, input().split()) n map(int, input().split()) map int input().split() ().split () input split k if k == 1:
        print(0)
    else:
        print(n-k) k == 1 k 1 print(0) print 0 print(n-k) print n-k n k if __name__ == '__main__':
    main() __name__ == '__main__' __name__ '__main__' main() main def main():
    n, k = map(int, input().split())
    if k == 1:
        print(0)
    else:
        print(n-k) def main():
    n, k = map(int, input().split())
    if k == 1:
        print(0)
    else:
        print(n-k) main
def main():
    n, k = map(int, input().split())
    if k == 1:
        print(0)
    else:
        print(n-k)


if __name__ == '__main__':
    main()