C# Öğrenci Ortalama Hesaplama

{string ad_soyad; int y1,y2,y3,s1,s2,s3; double ort; ad_soyad=Convert.ToString(txtad.Text); y1=Convert.ToInt32(txty1.Text); y2=Convert.ToInt32(txty2.Text); y3=Convert.ToInt32(txty3.Text); s1=Convert.ToInt32(txts1.Text); s2=Convert.ToInt32(txts2.Text); s3=