program ABC171_C
  character(11)::B
  integer(16)::N,cnt=1,i,j
  integer(16),allocatable::C(:)
  read(*,*)N
  do i=1,11
     if(N>26**i) then
        N=N-26**i
        cnt=cnt+1
     else
        allocate(C(cnt))
        C=97
        do j=1,cnt
           C(j)=mod(N,26)+C(j)-1
           if(C(j)==96) C(j)=122
           N=N/26
           if(N==0)  then
              if(cnt>1) then
                 do k=2,cnt
                    if(C(k)/=97) C(k)=C(k)+1
                 end do
              end if
              exit
           end if
        end do
        exit
     end if
  end do
  do i=1,cnt
     B(cnt+1-i:cnt+1-i)=char(C(i))
  end do
  B=adjustl(B)
  B=trim(B)
  write(*,'(a)')B(1:cnt)
end program ABC171_C