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 Rust (1.15.1) (judge verdict: Accepted)

use std::io::stdin;


fn is_prime(num: i32) -> bool {
    if num == 2 { return true }
    let n = num as f32;
    let r = n.sqrt().floor() as i32;
    for i in 2..(r+1) {
        if num % i == 0 { return false }
    }
    true
}

fn main() {
    let mut s = String::new();
    stdin().read_line(&mut s).unwrap();
    let lim: i32 = s.trim_right().parse().unwrap();
    for i in lim.. {
        if is_prime(i) {
            println!("{}", i);
            break;
        }
    }
}


#[test]
fn test() {
    assert_eq!(is_prime(2), true);
    assert_eq!(is_prime(3), true);
    assert_eq!(is_prime(12), false);
    assert_eq!(is_prime(29), true);
}