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 JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

'use strict'

function main(s) {

  const x = Number(s);

  let i = 0;
  let ans = 0;
  while (ans <= x) {
    i += 1;
    ans = i * i;
  }
  ans = (i - 1) * (i - 1);
  console.log(ans);
}

main(require("fs").readFileSync("/dev/stdin", "utf8"));