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>
#include <cstdlib>
#include <cmath>
#define rep(i,n) for (long long i=0; i < (n); ++i)
#define rep2(i,n,m) for(long long i=n;i<=m;i++)
using namespace std;
using ll = long long;
using P = pair<int,int>;
const ll INF=1e18 ;
inline void chmax(ll& a,ll b){a=max(a,b);}
inline void chmin(ll& a,ll b){a=min(a,b);}
int main() {
  int x ;
  cin >> x ;
  rep2(i,x,200000){
   int ans= 0;
    for(int j=2;j*j<=i;j++){
      if((i%j)==0) 
      ans= 1 ;
    }
  if(ans==0){
  cout<< i <<endl ;
  break ;
  }
  }
    return 0;
}