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 main() {
    let x: u64 = read();

    for n in x..100004 {
        let mut check = false;
        for i in 2..n - 1 {
            if n % i == 0 {
                check = true;
                break;
            }
        }
        if !check {
            println!("{}", n);
            return;
        }
    }
}

use std::io::stdin;
use std::io::Read;
use std::str::FromStr;

pub fn read<T: FromStr>() -> T {
    let cin = stdin();
    let cin = cin.lock();
    let token: String = cin
        .bytes()
        .map(|c| c.expect("failed to read char") as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().expect("failed to parse token")
}