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)

_isPrime = function(n) {
  if (n < 2) {
    return false
  }
  for (var i = 2; i*i <= n; i++) {
    if (n % i === 0) {
      return false
    }
  }
  return true
}

inp = require('fs').readFileSync('/dev/stdin', 'utf8').trim().split('\n')
x = inp.shift() * 1
while (true) {
    if (_isPrime(x)) {
        break;
    }
    x++
}
console.log(x)