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)

/* << IN THE NAME OF GOD >> */
#include <bits/stdc++.h>
using namespace std;



#define err(x) cerr << #x  << " = "<<  x << '\n'
#define out(x) cout << x << '\n'
#define forp(i, r, l) for(int i = int(r); i < int(l); i++)
#define forn(i, r, l) for(int i = int(r); i > int(l); i--)
#define FAST ios::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll ,ll> pll;
const int maxn = 1e5 + 120;
 

int x;
vector<bool> vec(maxn);
int main(){FAST;
    
    cin >> x;
    vec[1] = 1;
    for(int i = 2 ,a; i <= x; i++){
        a = i * i;
        while(a <= x)
            vec[a] = 1 ,a *= i;
    }
    forn(i ,x ,0)
        if(vec[i])
            return cout << i ,0;


   return 0;
}