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>
#define rep(i,n) for (int i = 0; i < (n); ++i)
using namespace std;
typedef long long ll;

int main(){
  int x;
  cin >> x;
  int a[100005];
 
  /* 判定フラグ */
  int flag;
 
  /* 素数かどうかを判定 */
  for(int i=x;i<=100003;++i ) {
    flag = 0;
    for(int j=2;j<i;++j ){
      if(i%j==0 ) {
        flag = 1;
        break;
      }
    }
    /* 判定結果を出力 */
    if(flag==0){
      cout << i << endl;
      break;
    }
  }
  return 0;
}