program main
  implicit none
  integer*8::N,i,modn,divn
  integer::res(10)
  data res/10*0/
  read *,N
  do i=1,10
     divn = N/26
     modn = MOD(N,26)
     res(i) = modn
     if(divn.eq.0) exit
     N    = divn
  end do

  do i=i,2,-1
     write(*,'(a)',advance='no'),ACHAR(ICHAR('A')+res(i)-1)
  end do
  write(*,'(a)'),ACHAR(ICHAR('A')+res(i))
end program main