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: Wrong Answer)

program main
	implicit none
    integer(8)::x,i,j,ans
    
    read(*,*)x
    ans=0
    
    do i=1,x
    	do j=2,x
        	if(i**j<=x .and. i**j>ans)then
            	ans=i**j
            end if
        end do
    end do
    write(*,*) ans
    stop
end program main