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