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