{-# OPTIONS_GHC -O3 #-}
{-# LANGUAGE ViewPatterns, ScopedTypeVariables #-}

import qualified Data.ByteString as B (getLine)
import qualified Data.ByteString.Char8 as C (readInt, words)
import qualified Data.Maybe as M (fromJust)

readInt = fst . M.fromJust . C.readInt

main = do
    (map readInt . C.words -> [n, k]) <- B.getLine
    putStrLn $ show $ if k > n then 0 else n - k
