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)

fn find_prime(frm : i32) -> i32 {
    let mut prime = 0;
    let mut i = frm;
    loop {
        let x = i as f64;
        let xx = x.sqrt().floor() as i32;
        //println!("{} {}", i,xx);
        let mut is_prime = true;
        for j in 2..(xx+1) {
            if i % j == 0 {
                is_prime = false;
                break;
            }
        }
        if is_prime {
            prime = i;
            break;
        }
        i += 1;
    }
    return prime;
}

use std::str::FromStr;

fn get_one<T : FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    return s.trim().parse().ok().unwrap();
}

fn get_vec<T : FromStr>() -> Vec<T> {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    return s.trim().split_whitespace().map(|e| e.parse().ok().unwrap()).collect();
}

fn main() {
    let n : i32 = get_one();
    let p = find_prime(n);
    println!("{}", p);
}