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 PHP7 (7.0.15) (judge verdict: Accepted)

<?php

class In {

	private $buf = [];
	private $count = 0;
	private $pointer = 0;

	public function nextLine() {
		$ret = '';
		if($this->hasNext()){
			while($this->hasNext()){
				$ret .= $this->next();
			}
		}else{
			$ret = trim(fgets(STDIN));
		}

		return $ret;
	}

	public function next() {
		if(!$this->hasNext()) {
			$str = trim(fgets(STDIN));
			$this->buf = explode(' ',$str);
			$this->count = count($this->buf);
			$this->pointer = 0;
		}

		return $this->buf[$this->pointer++];
	}

	public function hasNext() {
		return $this->pointer < $this->count;
	}

	public function nextInt() {
		return (int)$this->next();
	}

	public function nextDouble() {
		return (double)$this->next();
	}
}

class Out {
	public function println($str = '') {
		echo $str . PHP_EOL;
	}
}

$in = new In();
$out = new Out();

$X = $in->nextInt();
$t = $in->nextInt();

$out->println(max(0,$X-$t));

?>