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 9.2.1) (judge verdict: Accepted)

/*
 * FileName:     C
 * CreatedDate:  2020-06-25 22:40:43 +0900
 * LastModified: 2020-06-25 22:47:09 +0900
 */

#include <stdio.h>
#include <math.h>
#define s_m 100100
int box[s_m];
int main(void){
    int x;scanf("%d",&x);
    int y = x+100;
    for(int i=2;i<(int)sqrt(y);i++){
        for(int j=2;j*i<y;j++){
            if(box[i*j]==0){
                box[i*j]=1;
            }
        }
    }
    for(int i=x;i<s_m;i++){
        if(box[i]==0){
            printf("%d\n",i);
            return 0;
        }
    }
    return 0;
}