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 main()
{
	int i, j;
	int x;
	scanf("%d", &x);
	int flag;
	
	int cnt = 0;
	for (i = 2; i <= 1000000; ++i) {
		flag = 0;
		for (j = 2; j < i; ++j) {
			if (i % j == 0) {
				flag = 1;
				break;
			}
		}
		if (flag==0&&x == i) {
			printf("%d\n", x);
			return 0;
		}
		else if (flag==0&&x < i) {
			printf("%d\n", i);
			return 0;
		}
	}
	return 0;
}