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

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

if k == 1:
    print(0)
    exit()
n -= k
print (n)