a = list(map(int, input().split()))
if a[1] != 1:
    print(a[0] - a[1])
else:
    print(0) a = list(map(int, input().split())) a list(map(int, input().split())) list map(int, input().split()) map int input().split() ().split () input split if a[1] != 1:
    print(a[0] - a[1])
else:
    print(0) a[1] != 1 a[1] a 1 1 print(a[0] - a[1]) print a[0] - a[1] a[0] a 0 a[1] a 1 print(0) print 0 a = list(map(int, input().split())) list(map(int, input().split())) a
a = list(map(int, input().split()))
if a[1] != 1:
    print(a[0] - a[1])
else:
    print(0)