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 C (GCC 5.4.1) (judge verdict: Accepted)

#include<stdio.h>
#include<math.h>
int main()
{
    int x;
    scanf("%d", &x);
    int b, p;
    int max = 1;
    for (b = 2; b <= sqrt(x); b++)
    {
        for (p = 1;; p++)
        {
            if (pow(b, p) <= x)
            {
                if (pow(b, p) > max)
                    max = pow(b, p);
            }
            else
                break;
        }
    }
    printf("%d\n", max);
    return 0;
}