using System;

​

public class Program {

  public static void Main(string[] args) {

    decimal dNumber = 0;

    int ? num1 = null, num2 = null, num3 = null, num4 = null, num5 = null, num6 = null;

    string stringNum = null;

​

    num1 = 1;

    num2 = 3;

    num3 = 3;

    num4 = 3;

    num5 = 4;

    num6 = 4;

​

    if (num4 == null) {

      Console.WriteLine("uh oh");

    } else {

      dNumber = Convert.ToDecimal(num1 + num2 + num3 + num4);

      dNumber = dNumber / 4;

    }

​

    if (num5 == null) {

      string buffer = "buffered.";

    } else {

      dNumber = Convert.ToDecimal(num1 + num2 + num3 + num4 + num5);

      dNumber = dNumber / 5;

    }

​

    if (num6 == null) {

      string buffer = "buffered.";

    } else {

      dNumber = Convert.ToDecimal(num1 + num2 + num3 + num4 + num5 + num6);

      dNumber = dNumber / 6;

    }

    stringNum = Convert.ToString(dNumber);

​

    Console.WriteLine(stringNum);

  }

}