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;

typedef long long ll;

int main(){
	int n, ans=1;
	cin >> n;
	bool num[1001] = {false};
	for(int i = 2; i <= 1000; i++){
		int j = i;
		while(j*i <= 1000)num[j*i] = true, j *= i;
	}
	for(int i = 1; i <= n; i++)if(num[i])ans = i;
	cout << ans << endl;
    return 0;
}