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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <iostream>
#include <cmath>
using namespace std;

int main()
{
	long long x;
	cin >> x;

	if (x == 2) {
		cout << 2 << endl;
		return 0;
	}
	else if (x % 2 == 0) {
		x++;
	}
	bool flag;
	while (1) {
		flag = true;
		for (int i = 2; i <= (int)sqrt(x); i++) {
			if (x % i == 0) {
				flag = false;
				break;
			}
		}

		if (flag) {
			cout << x << endl;
			return 0;
		}

		x++;
	}

	return 0;
}