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: Time Limit Exceeded)

#include <bits/stdc++.h>
using namespace std;

int main() {
  int n;
  cin >> n;
  int f=0;
  if(n==2){
    cout << 2 << endl;
  }else{
    int a=0;
    while(a==0){
      if(n%2==1){
        for(int i=3;i<sqrt(n);i=i+2){
          if(n%i==0){
            f=1;
            i=n;
          }
        }
        if(f==1){
          n++;
        }else{
          cout << n << endl;
          a=1;
        }
      }
    }
  }
}