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.

Input

Input is given from Standard Input in the following format:
X

Output

Print the largest perfect power that is at most X.

Constraints

• 1 ≤ X ≤ 1000
• X is an integer.

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

见题面 Input 部分

见题面 Output 部分