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 OCaml (4.02.3) (judge verdict: Wrong Answer)

open Printf
open Scanf

let () =
        let s = read_line() in
        let rec iter i ans =
                if i = (String.length s) then
                        printf "%s\n" ans
                else if (i mod 2 = 0) then
                        iter (i + 1) (ans ^ (String.make 1 s.[i]))
                else
                        iter (i + 1) ans
        in iter 0 ""