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 i,j,x,np,p[100000];
  p[0]=2;
  np=1;
  for(i=3;i<101000;i+=2){
    for(j=1;j<np;j++){
      if(i%p[j]==0) break;
    }
    if(j==np){
      p[np]=i;
      np++;
    }
  }
  scanf("%d",&x);
  for(i=0;p[i]<x;i++);
  printf("%d",p[i]);
  return(0);
}