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-----
10

-----Sample Output-----
9

There are four perfect powers that are at most 10: 1, 4, 8 and 9.
We should print the largest among them, 9.

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