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 Python (3.8.2) (judge verdict: Accepted)

def solve():
  ans = 0
  X = int(input())
  lis = [False]*(X+1)
  lis[1] = True
  for b in range(2,X+1):
    p = 2
    while b**p<=X:
      lis[b**p] = True
      p += 1
  for i in range(X,-1,-1):
    if lis[i]==True:
      return i
print(solve())