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>

int main() {
  int a;
  scanf("%d",&a);
  if(a <=3) {
    printf("1\n");
    return 0;
  }
  int ans = 4;
  for(int i = 2; i <= a; i++) {
    int tmp = i*i;
    while(tmp <= a) {
      tmp *= i;
    }
    if(tmp/i != i) ans = ans > tmp/i ? ans : tmp/i;
  }
  printf("%d\n", ans);
  return 0;
}