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 (Clang 3.8.0) (judge verdict: Accepted)

#include <stdio.h>

int main(int argc, char *argv[]) {
  int x;
  int r, i;
  scanf("%d", &x);
  while(1) {
    r = 0;
    for (i = 2; i < x; i++) {
      if (x % i == 0) {
	r = 1;
	break;
      }
    }
    if (r == 0) break;
    x++;
  }
  printf("%d\n", x);
  return 0;
}