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)

import           Data.List
import           Control.Applicative
import           Control.Monad
import           Control.Monad.State

main = do
  (a : b : _) <- map (read :: String -> Int) . words <$> getLine
  print $ case a - b of
    n | n > 0     -> n
      | otherwise -> 0