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;
#define rep(i,n) for(int i=0;i<n;i++)
typedef long long ll;

int main(){
  int x;
  cin>>x;
  long long int a[100][100];
  for(int i=2;i<33;i++){
    for(int j=2;j<11;j++){
      if(pow(i,j)>x) break;
      a[i][j]=pow(i,j);
    }
  }
  int min=1000000;
 for(int i=2;i<33;i++){
    for(int j=2;j<11;j++){
      if(min>=x-a[i][j]){
        min=x-a[i][j];
      }
    }
  }
  cout<<x-min<<endl;
}