import numpy as np
#A = str(input())
#A = "ABCABC"
#N = int(input())
[N,K] = list(map(int,input().split()))
if K == 1:
    print(0)
else:
    print(N-K) import numpy as np numpy [N,K] = list(map(int,input().split())) [N,K] N K list(map(int,input().split())) list map(int,input().split()) map int input().split() ().split () input split 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
import numpy as np
#A = str(input())
#A = "ABCABC"
#N = int(input())
[N,K] = list(map(int,input().split()))
if K == 1:
    print(0)
else:
    print(N-K)