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 a = readLine()!!.toInt()

    val prime = ArrayList<Int>()
    prime.add(2)

    var x = 3
    while (prime.last() < a) {
        if (isPrime(x, prime)) prime.add(x)
        x += 2
    }
    println(prime.last())
}

fun isPrime(a: Int, p: List<Int>): Boolean {
    return p.takeWhile { it * it <= a }.all { a % it != 0}
}