import Data.List.Split
import Data.List

main = do
    a <- getContents
    let aa = splitOn " " $ head $ splitOn "\n" a
    let bb = read $ head aa :: Int
    let cc = read $ last aa :: Int
    --print bb
    --print cc
    let ans = if bb - cc <= 0 then 0 else bb - cc
    putStr $ show ans

