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: Accepted)

'use strict'

function main(s) {

  const x = Number(s);
  const nums = [...Array(31)].map((x, i) => i + 1);
  nums.shift();
  const max_ary = [1];

  for (let i = 0; i < nums.length; i++) {
    let j = 2;
    let n = nums[i];
    let max = Math.pow(n, j);
    if (max > x) continue;
    while (max <= x) {
      j += 1;
      max = Math.pow(n, j);
    }
    max = Math.pow(n, j - 1);
    max_ary.push(max);
  }

  const ans = Math.max(...max_ary);
  console.log(ans);
}

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