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 C (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>
int prime(int n);
int main(void) {
	int n,k;
	scanf("%d", &n);

	if (prime(n))
		printf("%d",n);
	else {
		for(k=n;prime(k)==0;k++){
		}
		printf("%d",k);
		}
	
	return 0;
}

/*素数を判定する関数
 * 素数であれば1を返し、素数でなければ0を返す
 */
int prime(int n) {
	int i; 
	
	for (i = 2; i < n; i++) {
		if (n % i == 0) {
			return 0;
		}
	}
	return 1;
}