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: Wrong Answer)

#include <stdio.h>

int hantei(int,int);

int main(void){
    int n;
    scanf("%d",&n);
    int i,j;
    for(i=n;i>0;i--){
        for(j=2;j<=i/2;j++){
            if(hantei(i,j)!=1){
                continue;
            }else{
                printf("%d\n",i);
                return 0;
            }
        }
    }
}


int hantei(int a,int b){
    if(a==1){
        return 1;
    }else if(a%b!=0){
        return 0;
    }else{
        a/=b;
        return hantei(a,b);
    }
}