import sys
sys.setrecursionlimit(1000000)
 
N,K = map(int,input().split())

if K == 1:
    print(0)
else:
    print(N-K) import sys sys sys.setrecursionlimit(1000000) sys.setrecursionlimit sys setrecursionlimit 1000000 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 N,K = map(int,input().split()) map(int,input().split()) N K = map(int,input().split()) map(int,input().split()) K
import sys
sys.setrecursionlimit(1000000)
 
N,K = map(int,input().split())

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