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<string.h>

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

	for (int i = X; i < 1000000; i++) {

		if (X == 2 || X == 3 || X == 5 || X == 7) {
			ans = X;
			break;
		}

		if (i % 2 == 0) {
			continue;
		}
		else if (i % 3 == 0) {
			continue;
		}
		else if (i % 5 == 0) {
			continue;
		}
		else if (i % 7 == 0) {
			continue;
		}
		else {
			for (int j = 11; j < i; j++) {
				if (i % j == 0) {
					flag = 1;
					break;
				}
			}
			if (flag != 0) {
				flag = 0;
				continue;
			}
		}
		ans = i;
		break;
	}

	printf("%d", ans);

	return 0;
}