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: Accepted)

my $X = <STDIN>;
my %h;
$h{1} = '';
foreach my $i (2..31) {
        foreach (2..31) {
                my $v = $_**$i;
                if ($v < 1001){
                        $h{$v} = '';
                } else {
                        last;
                }
        }
}
my $vv = 1;
foreach (sort {$a <=> $b} keys %h) {
        if ($_ <= $X) {
                $vv = $_;
        } else {
                last;
        }
}
print $vv;