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 <iostream>

int main(){
   int X;
   std::cin >> X;
   while(true){
      bool flag = true;
      for(int i=2; i*i<X; ++i){
	 if(X%i==0) {
	    flag = false;
	    break;
	 }
      }
      if(flag) {
	 std::cout << X << std::endl;
	 return 0;
      }
      ++X;   
   }
   return -1; 
}