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 9.2.1) (judge verdict: Accepted)

#include <iostream>
#include <numeric>
#include <cmath>
#include <limits>
#include <stdio.h>
#include <iomanip>
#include <string> // string, to_string, stoi
#include <vector> // vector
#include <algorithm> // min, max, swap, sort, reverse, lower_bound, upper_bound
#include <utility> // pair, make_pair
#include <tuple> // tuple, make_tuple
#include <cstdint> // int64_t, int*_t
#include <cstdio> // printf
#include <map> // map
#include <queue> // queue, priority_queue
#include <set> // set
#include <stack> // stack
#include <deque> // deque
#include <unordered_map> // unordered_map
#include <unordered_set> // unordered_set
#include <bitset> // bitset
#include <cctype> // isupper, islower, isdigit, toupper, tolower
using namespace std;
using ll = long long;
#define rep(i, n) for (long long i = 0; i < (long long)(n); i++)
ll Max(ll(a), ll(b), ll(c)) {
	return max(max(a, b), c);
}
ll Min(ll(a), ll(b), ll(c)) {
	return min(min(a, b), c);
}





int main() {

	ll X;
	cin >> X;
	ll an = 1;
	for (ll i = 2; i * i <= X; i++) {
		ll k = i * i;
		while (k <= X) {
			an = max(an, k);
			k *= i;
		}
	}
	cout << an << endl;
}