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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include<bits/stdc++.h>
using namespace std;

int power(int x,int y)
{
    int res=1;
    while(y>0)
    {
        if(y%2!=0)
            res=res*x;
        y/=2;
        x=x*x;
    }
    return res;
}
int A[1005]={0};
int main()
{
    A[1]=1;
    for(int i=2;i*i<=1000;i++)
    {
        int j=2;
        //cout<<i<<": \n";
        while(power(i,j)<=1000)
        {
            int in=power(i,j);
            A[in]=1;
            j++;
            //cout<<i<<" "<<j-1<<" "<<in<<" , ";
        }
        //cout<<endl;
    }
    /*for(int i=1;i<=1000;i++)
    {
        if(A[i]==1)
            cout<<i<<" ";
    }*/
    //cout<<endl;
    int n;
    cin>>n;
    while(A[n]==0)
    {
        n--;
    }
    cout<<n<<endl;
}