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 <bits/stdc++.h>
using namespace std;
using pii=pair<int,int>;
using ll=long long;

#define fi first
#define se second
#define pb push_back
#define rep(i,n) for(int i=0; i<(int)(n); i++)

int main() {

	int x;
	cin >> x;
	int y=x;
	
	while(1) {
		if (x == 2) {
			cout << 2 << endl;
			return 0;
		}
		for (int i=2; i<x; i++) {
			if (y % i == 0) {
				break;
			}
			if (i == x-1) {
				cout << y << endl;
				return 0;
			}
		}
		y += 1;
	}

  return 0;
}