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: Wrong Answer)

#include <stdio.h>

#define TRUE 0
#define FALSE 1
#define MAX 1000

int main(void){
  int i,j,x;
  
  int Exp[1000];
  
  for( Exp[0]=FALSE, i=1; i<MAX; i++){
    Exp[i] = FALSE;
  }
  
  for( i=2; i<MAX; i++){
    for( j=i*i; j<MAX; j *= i){
      Exp[j] = TRUE;
    }
  }
  
  scanf("%d",&x);
  
  for( i=x; i>0; i--){
    if( Exp[i] == TRUE ){
      printf("%d\n",i);
      return 0;
    }
  }
  
  return 0;
}