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 (1.15.1) (judge verdict: Wrong Answer)

fn main() {
    let mut buf = String::new();
    std::io::stdin().read_line(&mut buf).ok();
    let vec: Vec<&str> = buf.split_whitespace().collect();
    let a: i32 = vec[0].parse().unwrap();

    let x: [i32; 41] = [1, 4, 8, 9, 16, 25, 27, 32, 36, 49, 64, 81, 100, 121, 125, 128, 144, 169, 196, 216, 225, 243, 256, 289, 324, 343, 361, 400, 441, 484, 512, 529, 576, 625, 676, 729, 784, 841, 900, 961, 1000];
    let mut cnt: usize = 1;
    let mut done: bool = false;

    while !done{
        if x[40-cnt] <= a{
            println!("{:?}",x[40-cnt] );
            done = true;
        }
        cnt = cnt + 1;
    }

}