Problem:
Score : 200 points

Problem Statement

You are given a positive integer X.
Find the largest perfect power that is at most X.
Here, a perfect power is an integer that can be represented as b^p, where b is an integer not less than 1 and p is an integer not less than 2.

Constraints

1 ≤ X ≤ 1000

X is an integer.

Input

Input is given from Standard Input in the following format:

X

Output

Print the largest perfect power that is at most X.

Sample Input 1

10

Sample Output 1

9

There are four perfect powers that are at most 10: 1, 4, 8 and 9.
We should print the largest among them, 9.

Sample Input 2

1

Sample Output 2

1

Sample Input 3

999

Sample Output 3

961

Solution in Rust (1.42.0) (judge verdict: Accepted)

#![allow(unused_imports)]
#![allow(dead_code)]
use proconio::input;
use proconio::fastout;
#[macro_use] extern crate text_io;
use proconio::marker::*;
use std::mem;

#[fastout]
fn main() {
    input!{
        a:usize,
    }
    let mut ans:usize=1;
    for i in 2..a+1{
        let mut j=i*i;
        while j<=a{
            if 
            ans<j {
                ans=j;
            }
            j*=i;
        }
    }
    println!("{}",ans);
}