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 (GCC 5.4.1) (judge verdict: Accepted)

#include<stdio.h>

int main() {
    int X,i,flg;
    scanf("%d",&X);
    if(X == 2) {
	printf("%d\n", X);
	return 0;
    }	
    if(X%2 == 0) X++;
    while(1){
        flg = 0;	
	for(i = 3 ;i * i <= X; i+=2){
      	  if(X%i==0){
            flg = 1;
	    X+=2;
      	    break;
      	  }
        }
      if(flg == 0){	  
	  printf("%d\n",X);
        break;
      }
    }
    return 0;
}