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: Wrong Answer)

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>

int asc(const void* a, const void* b) {
    return *(int*)b - *(int*)a;
}
int main() {
    int x,flag=0;
    scanf("%d", &x);
   
    for (int i = x;flag==0 ; i++) {
        //printf("%d\n", i);

        if (i % 2) {
            for (int j = 3; ; j += 2) {
                if (i % j == 0)break;
                else if (j >= x - 1)flag = 1;
            }
        }
        else if (x == 2) flag = 1;
        if (flag) {
            printf("%d", i);
            break;
        }
    }
    
    return 0;
}