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: Wrong Answer)

import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		int ptr = 0;						
		int[] prime = new int[10000000];	
		Scanner stdIn = new Scanner(System.in);
		int st;
		do{
			st = stdIn.nextInt();
		}while(st<2||st>100000);
		int min = 0;
		prime[ptr++] = 2;					
		prime[ptr++] = 3;					

		for (int n = 5 ; n <= 1000000; n += 2) {		
			boolean flag = false;
			for (int i = 1; prime[i] * prime[i] <= n; i++) {
				if (n % prime[i] == 0) {	
					flag = true;
					break;						
				}
			}
			if (!flag) {						
				prime[ptr++] = n;
				if(n >= st) {
					min = n;
					break;
				}
			}
		}
			System.out.println(min);
	}
}