#!/usr/bin/env python3

n,k=map(int,input().split())


if k==1:
    print(0)
elif n==k:
    print(0)
elif n>k:
    print(n-k)
else:
    print(1)
 n,k=map(int,input().split()) n map(int,input().split()) map int input().split() ().split () input split k if k==1:
    print(0)
elif n==k:
    print(0)
elif n>k:
    print(n-k)
else:
    print(1) k==1 k 1 print(0) print 0 elif n==k:
    print(0) n==k n k print(0) print 0 elif n>k:
    print(n-k) n>k n k print(n-k) print n-k n k print(1) print 1 k=map(int,input().split()) map(int,input().split()) k n,k=map(int,input().split()) map(int,input().split()) n
#!/usr/bin/env python3

n,k=map(int,input().split())


if k==1:
    print(0)
elif n==k:
    print(0)
elif n>k:
    print(n-k)
else:
    print(1)

