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)

from collections import defaultdict

def readInt():
  return int(input())
def readInts():
  return list(map(int, input().split()))
def readChar():
  return input()
def readChars():
  return input().split()

x = readInt()
l = [0]*(x+1)
l[1]=1

for i in range(2,len(l)):
  if l[i]==0:
    j = i*i
    while 1:
      if j>len(l)-1:
        break
      else:
        l[j]=1
        j*=i


for i in range(len(l)-1,-1,-1):
  if l[i]==1:
    print(i)
    break