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 PyPy3 (2.4.0) (judge verdict: Accepted)

x = int(input()) # 入力が1つ
# map(int, input().split()) # 入力が複数
# [int(i) for i in input().split()] # 配列で数字

ans = 0
i = 1
p = 2
if x == 1:
    print(1)
else:
    while p <= 1000:
        while pow(p, i) <= x:
            if pow(p, i)<= x:
                ans = max(ans, pow(p, i))
            i += 1
        i = 2
        p += 1
    print(ans)