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 5.4.1) (judge verdict: Accepted)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
int main(void){
  int i,j;
  int n;
  int max=1;
  int f;
  int ans=1;
  scanf("%d",&n);
  j=(int)sqrt(n);
  for(i=2;i<=n;i++){
    max =1;
    f=0;
    while(max*i<=n){
      max *= i;
      f++;
    }
    if(max>ans && f>1){
      ans=max;
    }
  }
  printf("%d\n",ans);
  return 0;
}