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 Perl (v5.18.2) (judge verdict: Wrong Answer)

use v5.18;
use warnings;
sub read_line { chomp(my $str = <STDIN>); $str }
sub splited_read_line { split / /, read_line }

my $x = read_line;
my $max_num = 1;
for my $base (1 .. $x) {
  my $exponent = 2;
  while (1) {
    my $result = $base ** $exponent;
    last if $result > $x || $exponent > $x;
    $max_num = $result;
    $exponent++;
  }
}
say $max_num;