n,k = map(int,input().split())
if k == 1 or n - k <= 0:
    print(0)
elif n - k > 0:
    print(n - k) n,k = map(int,input().split()) n map(int,input().split()) map int input().split() ().split () input split k if k == 1 or n - k <= 0:
    print(0)
elif n - k > 0:
    print(n - k) k == 1 or n - k <= 0 k == 1 k 1 n - k <= 0 n - k n k 0 print(0) print 0 elif n - k > 0:
    print(n - k) n - k > 0 n - k n k 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
n,k = map(int,input().split())
if k == 1 or n - k <= 0:
    print(0)
elif n - k > 0:
    print(n - k)