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: Wrong Answer)

#include <stdio.h>

int main()
{
	int X;			/* ユーザーが指定する数値X */
	scanf("%d", &X);

	/* 
	 * 素数を2から探索しXと比べて出力するか否かを決定する
	 */

	int is_prime;		/* 素数かどうかの判定 */
	int value;		/* 判定する数値  */
	int index;		/* ループのインデックス */
	
	while(1){
		is_prime = 1;
		++value;
		for(index = 2; index < value; ++index){
			if(value % index == 0)
				is_prime = 0;
		}
		if((is_prime == 1) && (X < value)){
			printf("%d\n", value);
			break;
		}
	}
	return (0);
}