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 JavaScript (node.js v5.12) (judge verdict: Accepted)

var fs = require('fs');
var inn = parseInt(fs.readFileSync(0).toString());
function isPrime(n) {
    if(n <= 3) return n > 1;
    else if (n % 2 === 0 || n % 3 === 0) return false;
    var i = 5;
    while (Math.pow(i, 2) <= n) {
        if (n % i === 0 || n % (i + 2) === 0) return false;
        i += 6;
    }
    return true;
}
while (!isPrime(inn)) {
inn++;
}
console.log(inn);