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 main(void){
    int x,i,v;
    scanf("%d",&x);
    int a[x];
    for(i=0;i<x;i++){
        a[i]=0;
    }
    for(i=2;i<=x;i++){
        int v=i*i;
        while(v<=x){
            a[v]=1;
            v*=i;
        }
    }
    for(i=x-1;i>=1;i--){
        if(a[i]){
            printf("%d\n",i);
            return 0;
        }
    }
}