Sub ertert()
Dim x, s$, i&, k&
With Range("A1", Cells(Rows.Count, 1).End(xlUp))
    x = .Value
    For i = 1 To UBound(x)
        If Len(x(i, 1)) Then
            s = x(i, 1): k = 0
        Else
            k = k + 1
            x(i, 1) = s & "-" & k
        End If
    Next i
    .Value = x
End With
End Sub