program main
!    use iso_fortran_env
    implicit none

    integer(16) :: n, m
    character(:),allocatable :: txt
    character(26) :: alp

    alp = "zabcdefghijklmnopqrstuvwxy"

    read(*,*) n
    txt = ""

    do
        m = mod(n, 26)
        n = int(n / 26)
        if (m == 0) then
            n = n - 1
        endif
        txt = alp(m+1:m+1)//txt
        if (n == 0) exit
    enddo

    print *, trim(txt)

end program main