How to get total sum of rows at the footer of datagridview (windows application)

id    purticulars     debit    credit 
1      ammu           200        0
2     chinnu          300        0
3      annie           0        500
4      mittu           0        500

id    purticulars     debit    credit 
1      ammu           200        0
2     chinnu          300        0
3      annie           0        500
4      mittu           0        500
-----------------------------------------
       total          500       1000

for (int m = 1; m < dt.Columns.Count; m++)
                {
                    double sum = 0;
                    for (int j = 0; j < dt.Rows.Count; j++)
                    {
                        sum += Convert.ToDouble(dt.Rows[j][m]);
                        dataGridView1.Rows[dt.Rows.Count].Cells[m + 1].Value = sum.ToString();
                    }