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)

#[allow(unused_imports)]
use std::cmp::{max, min, Ordering};
#[allow(unused_imports)]
use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, VecDeque};
#[allow(unused_imports)]
use std::io::{stderr, stdin, stdout, BufRead, BufWriter, Read, StdoutLock, Write};
#[allow(unused_imports)]
use std::iter::FromIterator;
#[allow(unused_imports)]
use std::{i64, u64, usize};
#[allow(unused_macros)]
/// https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
macro_rules !input {(source =$s :expr ,$($r :tt ) *) =>{let mut iter =$s .split_whitespace () ;input_inner !{iter ,$($r ) *} } ;($($r :tt ) *) =>{let mut s ={use std ::io ::Read ;let mut s =String ::new () ;std ::io ::stdin () .read_to_string (&mut s ) .unwrap () ;s } ;let mut iter =s .split_whitespace () ;input_inner !{iter ,$($r ) *} } ;}
#[allow(unused_macros)]
macro_rules !input_inner {($iter :expr ) =>{} ;($iter :expr ,) =>{} ;($iter :expr ,$var :ident :$t :tt $($r :tt ) *) =>{let $var =read_value !($iter ,$t ) ;input_inner !{$iter $($r ) *} } ;}
#[allow(unused_macros)]
macro_rules !read_value {($iter :expr ,($($t :tt ) ,*) ) =>{($(read_value !($iter ,$t ) ) ,*) } ;($iter :expr ,[$t :tt ;$len :expr ] ) =>{(0 ..$len ) .map (|_ |read_value !($iter ,$t ) ) .collect ::<Vec <_ >>() } ;($iter :expr ,chars ) =>{read_value !($iter ,String ) .chars () .collect ::<Vec <char >>() } ;($iter :expr ,usize1 ) =>{read_value !($iter ,usize ) -1 } ;($iter :expr ,$t :ty ) =>{$iter .next () .unwrap () .parse ::<$t >() .expect ("Parse error" ) } ;}
#[allow(unused_macros)]
macro_rules !dbg {($($a :expr ) ,*) =>{writeln !(&mut stderr () ,concat !($(stringify !($a ) ," = {:?}, " ) ,*) ,$($a ) ,*) .unwrap () ;} }
#[allow(dead_code)]
pub fn prime(n: u64) -> Vec<bool> {
    let mut prime: Vec<bool> = vec![true; (n + 1) as usize];
    prime[0] = false;
    if n >= 1 {
        prime[1] = false;
    }
    let mut i = 2_usize;
    while i * i <= n as usize {
        if prime[i] {
            let mut j = i + i;
            while j <= n as usize {
                prime[j] = false;
                j += i;
            }
        }
        i += 1;
    }
    prime
}
#[allow(non_snake_case)]
#[allow(dead_code)]
fn main() {
    input! {
        x: usize,
    }
    let p = prime(1000_000);
    let mut x = x;
    while !p[x] {
        x += 1;
    }
    println!("{}", x);
}