import sys
import math
import bisect

def main():
    n, k = map(int, input().split())
    if k == 1:
        print(0)
    else:
        print(n - k)
    
if __name__ == "__main__":
    main() import sys sys import math math import bisect bisect 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
import sys
import math
import bisect

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