private void button1_Click(object sender, EventArgs e)

        {

            double n = Convert.ToDouble(textBox3.Text);

            double m = Convert.ToDouble(textBox2.Text);

            double q = Convert.ToDouble(textBox1.Text);

            richTextBox1.Text = "";

            double[] a = new double[2 * (int)q];

            Random r = new Random();

            for (int i = 0; i < 2 * q; i++)

            {

                double temp = r.Next((int)m, (int)n);

                a[i] = temp;

            }

            for (int i = 0; i < q; i++)

            {

                string c = "+";

                double b = a[i] + a[i + (int)q];

                if (b <= (int)n / 2)

                c = "*";

                if (b > (int)n / 2 && b <= (int)n)

                c = "+";

                if (b > (int)n && b <= (int)n * 1.5)

                c = "/";

                if (b > (int)n * 1.5 && b <= (int)n * 2 && a[i] > a[i + (int)q])

                c = "-";

                richTextBox1.AppendText(a[i].ToString() + (c) + a[i + (int)q].ToString() + ("=") + System.Environment.NewLine);

            }

        }

    }

}