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,y;
    int b,p;
    int ans=0;
    int calc;
    if(scanf("%d",&x)==1);

    y=(int)sqrt((double)x);

    for(b=1;b<=y;b++){
        for(p=2;p<10;p++){
            calc=(int)pow((double)b,(double)p);
            if(x<calc)break;
            if(ans<calc)ans=calc;
        }
    }
    printf("%d\n",ans);
}