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>
#define BUFSIZE 10000
#include<math.h>
#include<stdlib.h>
int a;
int flag=3;
int main (void){
	scanf("%d",&a);
	
if(a==2){
	printf("2");
}
		
	for(int i=0;i<BUFSIZE;i++){
	
	     for(int j=2;j<a+i;j++){
			 flag++;
			 if((a+i)%j==0){
              
				 break;
				 }
			if(flag==a+i && (a+i+1)%(a+i)!=0){
			  
				printf("%d",a+i);
	             exit(0);
			}
		 }
	
	}
	
}