private void button3_Click(object sender, EventArgs e)
        {
            yetgiris yetgrs = new yetgiris();

            yetgrs.Show();
            this.Hide();
        }
        private void pictureBox1_Click(object sender, EventArgs e)
        {
            yetgiris yetgrs = new yetgiris();

            yetgrs.Show();
            this.Hide();
        }