{-# LANGUAGE BangPatterns          #-}

import Control.Monad
import Control.Applicative
import Data.List as List
import Data.Set as Set



solve:: Int -> Int -> Int
solve x t
    | x >= t = x - t
    | otherwise = 0

main :: IO()
main = do
    [x, t] <- List.map read . words <$> getLine :: IO [Int]
    let s = solve x t
    print s
