Sub resizeMerge()

    Dim lRow                  As Long
    Dim lCount                As Long
    Dim lLastRow              As Long

    lRow = 1

    ' change to your last row
    lLastRow = 25

    Do While lRow <= lLastRow
        With Cells(lRow, "A")
            If .MergeCells Then
                lCount = .MergeArea.Cells.Count
                .UnMerge
                If lCount > 2 Then .Resize(lCount - 1).Merge
            End If
        End With
        lRow = lRow + lCount
    Loop
End Sub