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.*;
public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		TreeSet<Integer> prime = new TreeSet<>();
		prime.add(2);
		prime.add(3);
		for(int i = 5; i <= 100003; i+=2) {
			boolean isprime = true;
			for(int j = 2; j*j <= i; j++) {
				if(i % j == 0) {
					isprime = false;
					break;
				}
			}
			if(isprime)
				prime.add(i);
		}
		System.out.println(prime.higher(sc.nextInt()-1));

	}

}