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 main() {
    let mut buf = String::new();
    stdin().read_line(&mut buf).unwrap();
    let int: i32 = buf.trim().parse().unwrap();

    println!("{}", solve(int));
}

fn solve(mut int: i32) -> i32{
    if int == 2 || int == 3 {
        return int;
    }
    if int == 4{
        return 5;
    }

    loop{
        if is_prime(int){
            return int;
        }

        int += 1;
    }
}

fn is_prime(num: i32) -> bool{
    for iter in 2..num/2 {
        if num % iter == 0{
            return false;
        }
    }
    true
}