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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int X = sc.nextInt();

        for (int i = X; i < X * 2; i++)
            if (isPrime(i)) {
                System.out.println(i);
                return;
            }

    }

    static boolean isPrime(int num) {
        if (num == 1 || num == 2) return true;
        if (num % 2 == 0) return false;

        for (int i = 3; i < Math.sqrt(num); i += 2)
            if (num % i == 0) return false;

        return true;
    }
}