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: Accepted)



fn main(){
    let n:i32 = getline().trim().parse().unwrap();
    let mut best = 1;
    for x in 2..n {
        for y in 2..n {
            let z = x.pow(y as u32);
            if z > n { break; }
            if best < z { best = z; }
        }
    }
    println!("{}", best);
}

fn getline() -> String{
    let mut r = String::new();
    std::io::stdin().read_line(&mut r).ok();
    return r;
}