program main
 
  implicit none
 
  integer :: l 
  integer :: i,j ,vn
  real(8)    :: v, tmp
  
  read(*,*) l
  
  v = 0e0 
  vn = 10
  do i = 1, l*vn 
    do j = 1, l*vn-i
      tmp = real(l*vn-i-j,kind=8)
      tmp = real(i,kind=8)*real(j,kind=8)*tmp &
          / real(vn,kind=8)/real(vn,kind=8)/real(vn,kind=8)
      if ( tmp > v ) then
        v = tmp
      end if
    end do
  end do

  print*, v
  
end program main
