Console Application-Use of Select case

public void Main() { int s1 = 0; int s2 = 0; int s3 = 0; int tot = 0; double per = 0; Console.WriteLine("Enter the mark of First Subject out of 100"); s1 = Console.ReadLine(); Console.WriteLine("Enter the mark of Second Subject out of 100"); s2 = Console.ReadLine(); Console.WriteLine("Enter the mark of Third Subject out of 100"); s3 = Console.ReadLine(); tot = s1 + s2 + s3; per = (tot / 300) * 100; Console.WriteLine("Your Total is:=>" + tot); Console.WriteLine("your Percentage is:=>" + per); switch ((per)) { case // ERROR: Case labels with binary operators are unsupported : LessThan 40: Console.WriteLine("Grade:=>Fail"); Console.ReadLine(); break; case 40: case 41: case 42: case 43: case 44: case 45: case 46: case 47: case 48: case 49: case 50: Console.WriteLine("Grade:=>Second Class"); Console.ReadLine(); break; case 50: case 51: case 52: case 53: case 54: case 55: case 56: case 57: case 58: case 59: case 60: Console.WriteLine("Grade:=>First Class"); Console.ReadLine(); break; case // ERROR: Case labels with binary operators are unsupported : GreaterThan 70: Console.WriteLine("Grade:=>Distionction"); Console.ReadLine(); break; } }