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)

#define _GLIBCXX_DEBUG
#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define rep(i,N) for(int i = 0;i < (int)(N);i++)
int main(){
  int x;
  cin>>x;
  while(1){
    bool ok=true;
    for(int i=2; i<x; ++i){
      if(x%i==0){
        ok=false;
        break;
      }
    }
    if(ok) break;
    ++x;
  }
  cout<<x<<endl;
}