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 (1.42.0) (judge verdict: Accepted)

fn main() {
    let mut buf = String::new();
    std::io::stdin().read_line(&mut buf).expect("stdin read error");
    let mut num: i32 = buf.trim().parse().expect("parse error");

    let ans = loop {
        let end: i32 = (num as f64).sqrt() as i32;
        let mut is_prime = true;
        for i in 2..end {
            if num % i == 0 {
                is_prime = false;
            }
        }
        if is_prime {
            break num
        }
        num += 1;
    };
    println!("{}", ans);
}