public static void Main()
Console.WriteLine("Hello World");
ValidateRoutingNumber("102000021");
ValidateRoutingNumber("987654329");
ValidateRoutingNumber("102023621");
public static void ValidateRoutingNumber(string routingNumber)
string weighingFactor = "37137137";
double sum = Enumerable.Zip(weighingFactor, routingNumber, (wf, rn) => (wf - 48) * (rn - 48)).Sum();
double expectedcheckDigit = Math.Ceiling(sum / 10) * 10 - sum;
long actualCheckDigit = long.Parse(routingNumber) % 10;
if (expectedcheckDigit != actualCheckDigit)
Console.WriteLine($"{routingNumber} isInvalid_Routing_Number");
Console.WriteLine($"{routingNumber} is Valid_Routing_Number");