Problem:
Score: 300 points

Problem Statement

Find the minimum prime number greater than or equal to X.

Notes

A prime number is an integer greater than 1 that cannot be evenly divided by any positive integer except 1 and itself.

For example, 2, 3, and 5 are prime numbers, while 4 and 6 are not.

Constraints

2 \le X \le 10^5

All values in input are integers.

Input

Input is given from Standard Input in the following format:

X

Output

Print the minimum prime number greater than or equal to X.

Sample Input 1

20

Sample Output 1

23

The minimum prime number greater than or equal to 20 is 23.

Sample Input 2

2

Sample Output 2

2

X itself can be a prime number.

Sample Input 3

99992

Sample Output 3

100003

Solution in PHP7 (7.0.15) (judge verdict: Accepted)

<?php
// Your code here!

function primeNumber($target) {
    $limit = ceil(sqrt($target));
    $res = NULL; 
    for($i=2;$i<=$limit ;$i++) {
        if($target%$i == 0) { 
            $res = $i;
            break;
        }
    }
    if ($res == NULL) { 
        return TRUE;
    }else { ////$resがNULLでない場合。(素数でない場合。)
        return FALSE;
    }
}

fscanf(STDIN,"%d",$x);
if($x == 2){
    echo "2";
    exit();
}

while(true){
    if(primeNumber($x)){
        echo $x;
        break;
    }else{
        $x++;
    }
}