program one_quadrillion_and_one_dalmatians
  implicit none
  integer(8) :: n
  integer :: i = 0, k(11) = 0
  read(*,*) n
  do while (n > 0)
    i = i + 1
    k(i) = int(mod(n - 1, 26) + 1) + 96
    n = n / 26
  end do
  do while (i > 0)
    write(*,'(a)',advance='no') achar(k(i))
    i = i - 1
  end do
  write(*,*)
end program one_quadrillion_and_one_dalmatians