Sub merge()
    Dim i As Integer
    Dim i2 As Integer
    Dim i3 As Integer
    i = Range("B1")
    i2 = Range("B2")
    i3 = Range("B3")
    Range("A1:A" & i).merge
    Range("A" & (i + 1) & ":A" & (i + i2)).merge
    Range("A" & (i + i2 + 1) & ":A" & (i + i2 + i3)).merge
End Sub