int giaithua(int n)
        {
            int e = 1;
            for (int j = 1; j <= n; j++)
            {
                e = e * j;
            }
            return e;
        }

        Random rr = new Random();
        String t1 = "1: ";
        String t2 = "2: ";
        String t3 = "3: ";
        String t4 = "4: ";
        String t5 = "5: ";
        String t6 = "6: ";
        private void button1_Click(object sender, EventArgs e)
        {
            int n = rr.Next(1, 7);
            int n1 = 0; int n2 = 0; int n3 = 0;
            int n4 = 0; int n5 = 0; int n6 = 0;
            switch 👎
            {
                case 1: n1++; break;
                case 2: n2++; break;
                case 3: n3++; break;
                case 4: n4++; break;
                case 5: n5++; break;
                case 6: n6++; break;
            }


            for (int k = 0; k < n1; k++)
                t1 += "x";

            for (int k = 0; k < n2; k++)
                t2 += "x";

            for (int k = 0; k < n3; k++)
                t3 += "x";

            for (int k = 0; k < n4; k++)
                t4 += "x";

            for (int k = 0; k < n5; k++)
                t5 += "x";

            for (int k = 0; k < n6; k++)
                t6 += "x";

            label2.Text = t1;
            label3.Text = t2;
            label4.Text = t3;
            label5.Text = t4;
            label6.Text = t5;
            label7.Text = t6;
        }

        private void button2_Click(object sender, EventArgs e)
        {
            if (comboBox1.SelectedIndex == 3)
                label10.Text = "Right";
            else
                label10.Text = "Wrong";
        }

        int sx = 0;
        int sy = 0;
        int dir = 4;

        private void timer1_Tick(object sender, EventArgs e)
        {
            pictureBox1.Left += sx;
            pictureBox1.Top += sy;
            if (pictureBox1.Left <= 3 && dir == 4)
            {
                sx = 0;
                sy = 10;
                dir = 1;

            }
            if (pictureBox1.Left >= (groupBox1.Width - pictureBox1.Width) && dir == 2)
            {
                sx = 0;
                sy = -10;
                dir = 3;

            }

            if (pictureBox1.Top <= 3 && dir == 3)
            {
                sx = -10;
                sy = 0;

                dir = 4;

            }

            if (pictureBox1.Top >= (groupBox1.Height - pictureBox1.Height) && dir == 1)
            {
                sx = 10;
                sy = 0;

                dir = 2;
            }
        }

        private void button3_Click(object sender, EventArgs e)
        {
            timer1.Enabled = true;
        }

        private void button4_Click(object sender, EventArgs e)
        {
            timer1.Enabled = false;
        }

        int a,b;

        private void button6_Click(object sender, EventArgs e)
        {
            a = Convert.ToInt16(textBox1.Text);
            b = Convert.ToInt16(textBox2.Text);
            label14.Text = " " + a + b;
        }

        private void button7_Click(object sender, EventArgs e)
        {
            String[,] eu =
          {
{"Austria","January 1, 1995","Yes","Yes"},
{"Belgium","March 25, 1957","Yes","Yes"},
{"Bulgaria","January 1, 2007","No","No"},
{"Croatia","July 1, 2013","No","No"},
{"Cyprus","May 1, 2004","No","Yes"},
{"Czech Republic","May 1, 2004","Yes","No"},
{"Denmark","January 1, 1973","Yes","No"},
{"Estonia","May 1, 2004","Yes","Yes"},
{"Finland","January 1, 1995","Yes","Yes"},
{"France","March 25, 1957","Yes","Yes"},
{"Germany","March 25, 1957","Yes","Yes"},
{"Greece","January 1, 1981","Yes","Yes"},
{"Hungary","May 1, 2004","Yes","No"},
{"Ireland","January 1, 1973","No","Yes"},
{"Italy","March 25, 1957","Yes","Yes"},
{"Latvia","May 1, 2004","Yes","Yes"},
{"Lithuania","May 1, 2004","Yes","Yes"},
{"Luxembourg","March 25, 1957","Yes","Yes"},
{"Malta","May 1, 2004","Yes","Yes"},
{"Netherlands","March 25, 1957","Yes","Yes"},
{"Poland","May 1, 2004","Yes","No"},
{"Portugal","January 1, 1986","Yes","Yes"},
{"Romania","January 1, 2007","No","No"},
{"Slovakia","May 1, 2004","Yes","Yes"},
{"Slovenia","May 1, 2004","Yes","Yes"},
{"Spain","January 1, 1986","Yes","Yes"},
{"Sweden","January 1, 1995","Yes","No"},
{"United Kingdom","January 1, 1973","No","No"}};


            for (int i = 0; i < 28; i++)
            {
                if (listBox1.Text == eu[i, 0])
                    richTextBox1.Text = "Country\tEu access date\t Schengen Area member\tEurozone member\n" + eu[i, 0] + "\t" + eu[i, 1] + "\t" + eu[i, 2] + "\t\t\t" + eu[i, 3];
            }

        }

        private void button5_Click(object sender, EventArgs e)
        {
            a = Convert.ToInt16(textBox1.Text);
            b = Convert.ToInt16(textBox2.Text);
            label13.Text = " "+ a * b;

        }

        private void button8_Click(object sender, EventArgs e)
        {
            int l1, l2, l3, l4;
            while (true)
            {
                l1 = rr.Next(1, 14);
                l2 = rr.Next(1, 14);
                l3 = rr.Next(1, 14);
                l4 = rr.Next(1, 14);
                if (l1 != l2 && l1 != l3 && l1 != l4 && l2 != l3 && l2 != l4 && l3 != l4)
                    break;
            }
            hai(l1, pictureBox2);
            hai(l2, pictureBox3);
            hai(l3, pictureBox4);
            hai(l4, pictureBox5);
        }

        private void button9_Click(object sender, EventArgs e)
        {
            int o, p;
            o = Convert.ToInt16(textBox3.Text);
            p = Convert.ToInt16(textBox4.Text);

            label17.Text = (giaithua(o) / (giaithua(p) * giaithua(o - p))).ToString();
        }

        private void hai(int l, PictureBox k)
        {
            switch (l)
            {
                case 1: k.Image = Image.FromFile("C:\\Users\\co1601384\\Downloads\\1.JPG"); break;
                case 2: k.Image = Image.FromFile("C:\\Users\\co1601384\\Downloads\\2.JPG"); break;
                case 3: k.Image = Image.FromFile("C:\\Users\\co1601384\\Downloads\\3.JPG"); break;
                case 4: k.Image = Image.FromFile("C:\\Users\\co1601384\\Downloads\\4.JPG"); break;
                case 5: k.Image = Image.FromFile("C:\\Users\\co1601384\\Downloads\\5.JPG"); break;
                case 6: k.Image = Image.FromFile("C:\\Users\\co1601384\\Downloads\\6.JPG"); break;
                case 7: k.Image = Image.FromFile("C:\\Users\\co1601384\\Downloads\\7.JPG"); break;
                case 8: k.Image = Image.FromFile("C:\\Users\\co1601384\\Downloads\\8.JPG"); break;
                case 9: k.Image = Image.FromFile("C:\\Users\\co1601384\\Downloads\\9.JPG"); break;
                case 10: k.Image = Image.FromFile("C:\\Users\\co1601384\\Downloads\\10.JPG"); break;
                case 11: k.Image = Image.FromFile("C:\\Users\\co1601384\\Downloads\\J.JPG"); break;
                case 12: k.Image = Image.FromFile("C:\\Users\\co1601384\\Downloads\\Q.JPG"); break;
                case 13: k.Image = Image.FromFile("C:\\Users\\co1601384\\Downloads\\K.JPG"); break;
            }