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.lang.Math.sqrt

fun main(args: Array<String>) {
    var x = readInt()
    while (!isPrime(x)) {
        x++
    }
    println(x)
}


// Tools
fun readString() = readLine()!!
fun readInt() = readLine()!!.toInt()
fun readLong() = readLine()!!.toLong()
fun readStringList() = readLine()!!.split(" ")
fun readIntList() = readLine()!!.split(" ").map(String::toInt)
fun readLongList() = readLine()!!.split(" ").map(String::toLong)

// 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 = sqrt(num.toDouble())
    var i = 3
    while (i <= sqrtNum) {
        if (num % i == 0) return false
        i += 2
    }
    return true
}