How to prevent Datagridview from selecting the first cell on opening

public partial class Form1 : Form
    {
        private Random rnd;
        private int nSize = 4;

        public Form1()
        {
            InitializeComponent();
            rnd = new Random();
            for (int c = 0; c < nSize; c++)
            {
                this.dataGridView1.Columns.Add("Col" + c.ToString(), "Col" + c.ToString());
            }
        }

        private void buttonImport_Click(object sender, EventArgs e)
        {
            this.dataGridView1.Rows.Clear();
            int n = this.dataGridView1.Columns.Count;
            string[] nums;
            for (int r = 0; r < nSize; r++)
            {
                nums = new string[n];
                for (int c = 0; c < n; c++)
                {
                    nums[c] = (rnd.Next(-10, 10)).ToString();
                }
                this.dataGridView1.Rows.Add(nums);
                
            }
            ColorCells();
        }

        private void ColorCells()
        {
            int n = this.dataGridView1.Columns.Count;
            for (int r = 0; r < nSize; r++)
            {
                for (int c = 0; c < n; c++)
                {
                    string val = (string) this.dataGridView1.Rows[r].Cells[c].Value;
                    int v;
                    if(Int32.TryParse(val, out v) == false) continue;

                    if(v<0)
                        this.dataGridView1.Rows[r].Cells[c].Style.BackColor = Color.Red;
                    else
                        this.dataGridView1.Rows[r].Cells[c].Style.BackColor = Color.White;
                }
                
            }
        }
    }