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"
#include "stdarg.h"
#include "math.h"
#include "limits.h"

#define SWAP(type,a,b) do{type c=a;a=b;b=c;}while(0)
#define MAX(a,b) (((a)>(b))?(a):(b))
#define MIN(a,b) (((a)<(b))?(a):(b))
#define DEBUG(format,a) do{printf(#a" : "#format,a);}while(0)


int main() {
	int a,ans=0;
	scanf("%d", &a);

	int c = 0;
	if (a == 2) {
		printf("%d", 2);
	}else {
		while (1) {
			for (int i = 2;i < a + c;i++) {
				if ((a + c) % i == 0)break;
				else if (i == a + c - 1) {
					ans = a + c;
					break;
				}
			}
			if (ans != 0)break;
			c++;
		}
		printf("%d", ans);
	}

	return 0;
}