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 Fortran (GNU Fortran 9.2.1) (judge verdict: Accepted)

program prob3
    implicit none
    integer::X,i,j,k,ans
    integer::v(1000)
    read(*,*) X
    v = 0
    do i = 1, 34
        do j = 2,10
            if(i**j > 1000)then
                exit
            else
                v(i**j) = 1
            end if
        end do
    end do

    do i = 1,X
        if(v(i) == 1) then
            ans = i
        end if
    end do

    write(*,*) ans

end program