private void Display_Click(object sender, EventArgs e)
{
  listBox1.Items.Clear();
  listBox2.Items.Clear();
  foreach (int j in a)
     listBox1.Items.Add(j.ToString());
  for (int j = a.Length - 1; j >= 0; j--)
     listBox2.Items.Add(a[j].ToString());
  Display.Enabled = false;
  textBox1.Focus();
}
