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>
#include <math.h>

int prime(long int n)
{
    if(n==2)
       return 1;
       
    else if(n%2==0 || n<2)
        return 0;
        
    else
      {
          long int i;
          for(i=3;i<=sqrt(n);i+=2)
            {
                if(n%i==0)
                    return 0; 
            }
            
            return 1;
             
      }
}
int main(void) {
	long int x;
	scanf("%ld",&x);
	long int i;
	for(i=x;;++i)
	  {
	      if(prime(i))
	         break;
	  }
	  printf("%ld\n",i);
	return 0;
}