Problem:
Score : 100 points

Problem Statement

We have a sandglass that runs for X seconds. The sand drops from the upper bulb at a rate of 1 gram per second. That is, the upper bulb initially contains X grams of sand.

How many grams of sand will the upper bulb contains after t seconds?

Constraints

1≤X≤10^9

1≤t≤10^9

X and t are integers.

Input

The input is given from Standard Input in the following format:

X t

Output

Print the number of sand in the upper bulb after t second.

Sample Input 1

100 17

Sample Output 1

83

17 out of the initial 100 grams of sand will be consumed, resulting in 83 grams.

Sample Input 2

48 58

Sample Output 2

0

All 48 grams of sand will be gone, resulting in 0 grams.

Sample Input 3

1000000000 1000000000

Sample Output 3

0

Solution in Haskell (GHC 7.10.3) (judge verdict: Accepted)

{-# LANGUAGE BangPatterns #-}
import Control.Applicative((<$>))
import Control.Monad
import Data.Map ((!))
import qualified Data.Map as M
import qualified Data.List as L
import Data.Maybe (catMaybes)
-- import qualified Data.Char as C
-- import qualified Data.IntSet as I
import Debug.Trace
--------------------------------------------
readInt    = read :: String -> Int
getInt     = readInt <$> getLine
getIntList = map readInt . words <$> getLine
int2bin 0 =  []
int2bin n =  n `mod` 2 : int2bin (n `div` 2)
----------------------------------------------

main :: IO ()
main = do
  [x,t] <- getIntList
  print $ (x - t) `max` 0