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: Wrong Answer)

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

int x;

int main(){
//	cin.tie(0);
//	ios::sync_with_stdio(false);
	cin >> x;
	for(int i=x; i>=1; --i){
		int t = 0;
		for(int j=2; j<i; ++j)
			if(i % j == 0)
				++t;
		if(i == 1 || t == 1){
			cout << i << "\n";
			break;
		}
	}
}