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) {
		try (Scanner sc = new Scanner(System.in)) {
			int x = sc.nextInt();

			if (x == 2) {
				System.out.println(2);
				return;
			}

			if (x % 2 == 0) {
				x++;
			}

			do {
				if (isPrime(x)) {
					System.out.println(x);
					return;
				}
				x += 2;
			} while(true);
		}
	}

	private static boolean isPrime(int n) {
		for (int i = 3; i < Math.sqrt(n); i++) {
			if (n % i == 0) {
				return false;
			}
		}
		return true;
	}
}