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: Time Limit Exceeded)

#include <stdio.h>

int i;

int main(void)
{
    int X,E,ary[1000],min,ans=1;
    scanf("%d",&X);
    min=X;
    for(i=0;i<X;i++)
    {
        E=1;
        while(X>=E)
        {
            E*=i;
        }
        E/=i;
        ary[i]=X-E;
        if(min>ary[i])
        {
            min=ary[i];
            ans=E;
        }
    }
    printf("%d",ans);
    
    return 0;
    
}