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 <math.h>
typedef long long int ll;

int main(void){
  char buf[40];
  ll x;
  fgets(buf, 40, stdin);
  sscanf(buf, "%ld", &x);
  int b = 1;
  while(b){
    ll n = (int)sqrt(x) + 1;
    int bb = 0;
    for(ll i = 2; i <= n; i++){
      if(x % i == 0) bb = 1;
    }
    if(bb == 0) b = 0;
    x++;
  }
  printf("%lld\n", --x);
  return 0;
}