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>
typedef long long ll;
typedef long double ld;
using namespace std;

ll inf=9223372036854775806;

int main()
{
	//freopen("input.txt","r",stdin);freopen("output.txt","w",stdout);
	ios_base::sync_with_stdio(false); cin.tie(0);
	int i,j,n;
	bool p[1001];
	fill(p,p+1001,false);
	p[1]=true;
	for (i=2;i<=32;i++){
		for (j=2;pow(i,j)<=1000;j++){
			p[(int)(pow(i,j)+0.1)]=true;
		}
	}
	cin>>n;
	while (p[n]==false){
		n--;
	}
	cout<<n;
	return 0;
}