public static void Main()
Console.WriteLine("Enter The First Grade: ");
int gradeSt = int.Parse(Console.ReadLine());
Console.WriteLine("Enter The Second Grade: ");
int gradeNd = int.Parse(Console.ReadLine());
Console.WriteLine("Enter The Third Grade: ");
int gradeTh = int.Parse(Console.ReadLine());
int average = (gradeSt+gradeNd+gradeTh)/3;
Console.WriteLine("Your Average Is "+average);
Console.WriteLine("Your Average Is Under 90");