Add all borders on cells including center borders in excel using C# excel interop

Question

I tried making an excel file with borders on its cells. I tried the following code:

xlWorksheet.Range[xlWorksheet.Cells[13, 1], xlWorksheet.Cells[13,14]]
    .BorderAround(Excel.XlLineStyle.xlContinuous,
    Excel.XlBorderWeight.xlMedium);

but it is giving me the following output:

How will I add all borders of cells within specified range including the middle borders?