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 Kotlin (1.0.0) (judge verdict: Accepted)

import java.util.*

fun main(args: Array<String>) {
    val sc = Scanner(System.`in`)
    val x = sc.nextInt()
    println(problem149c(x))
}

fun problem149c(x: Int): Int {
    /**
     * 素数判定
     */
    fun isPrime(num: Int): Boolean {
        if (num < 2) return false
        if (num == 2) return true
        if (num % 2 == 0) return false

        val sqrtNum = Math.sqrt(num.toDouble()).toInt()
        for (i in 3..sqrtNum step 2) {
            if (num % i == 0) return false
        }
        return true
    }
    var x = x
    while (true) {
        if (isPrime(x)) return x
        x++
    }
}