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>

int i,j;

int main(void)
{
    int X,E,ans=1,key=0;
    scanf("%d",&X);
    for(i=X;i>0;i--)
    {
        for(j=2;j<i;j++)
        {
            E=i;
            while(E%j==0)
            {
                E/=j;
            }
            if(E==1)
            {
                key=1;
                break;
            }
        }
        if(key==1)
        {
            ans=i;
            break;
        }
            
    }
    printf("%d",ans);
    
    return 0;
    
}