09_SumOfSubsetIs0

using System;

class SumOfSubsetIs0
{
    static void Main()
    {
        int a;
        int b;
        int c;
        int d;
        int e;
        bool flagSum = false;

        Console.Write("Please enter the first number: ");
        string firstStr = Console.ReadLine();

        Console.Write("Please enter the second number: ");
        string secondStr = Console.ReadLine();

        Console.Write("Please enter the third number: ");
        string thirdStr = Console.ReadLine();

        Console.Write("Please enter the fourth number: ");
        string fourthStr = Console.ReadLine();

        Console.Write("Please enter the fifth number: ");
        string fifthStr = Console.ReadLine();

        if (!int.TryParse(firstStr, out a))
        {
            Console.WriteLine("Invalid number: {0}", firstStr);
        }
        else if (!int.TryParse(secondStr, out b))
        {
            Console.WriteLine("Invalid number: {0}", secondStr);
        }
        else if (!int.TryParse(thirdStr, out c))
        {
            Console.WriteLine("Invalid number: {0}", thirdStr);
        }
        else if (!int.TryParse(fourthStr, out d))
        {
            Console.WriteLine("Invalid number: {0}", fourthStr);
        }
        else if (!int.TryParse(fifthStr, out e))
        {
            Console.WriteLine("Invalid number: {0}", fifthStr);
        }
        else
        {
            // Combination with 5 numbers
            if (a + b + c + d + e == 0)
            {
                flagSum = true;
            }

            // Start of combination with 4 numbers
            else if (a + b + c + d == 0)
            {
                flagSum = true;
            }
            else if (a + b + c + e == 0)
            {
                flagSum = true;
            }
            else if (a + c + d + e == 0)
            {
                flagSum = true;
            }
            else if (a + b + d + e == 0)
            {
                flagSum = true;
            }
            else if (b + c + d + e == 0)
            {
                flagSum = true;
            }

            // Start of combination with 3 numbers
            else if (a + b + c == 0)
            {
                flagSum = true;
            }
            else if (a + b + d == 0)
            {
                flagSum = true;
            }
            else if (a + b + e == 0)
            {
                flagSum = true;
            }
            else if (a + c + d == 0)
            {
                flagSum = true;
            }
            else if (a + c + e == 0)
            {
                flagSum = true;
            }
            else if (a + d + e == 0)
            {
                flagSum = true;
            }
            else if (b + c + d == 0)
            {
                flagSum = true;
            }
            else if (b + c + e == 0)
            {
                flagSum = true;
            }
            else if (b + d + e == 0)
            {
                flagSum = true;
            }
            else if (c + d + e == 0)
            {
                flagSum = true;
            }

            // Start of combination with 2 numbers
            else if (a + b == 0)
            {
                flagSum = true;
            }
            else if (a + c == 0)
            {
                flagSum = true;
            }
            else if (a + d == 0)
            {
                flagSum = true;
            }
            else if (a + e == 0)
            {
                flagSum = true;
            }
            else if (b + c == 0)
            {
                flagSum = true;
            }
            else if (b + d == 0)
            {
                flagSum = true;
            }
            else if (b + e == 0)
            {
                flagSum = true;
            }
            else if (c + d == 0)
            {
                flagSum = true;
            }
            else if (c + e == 0)
            {
                flagSum = true;
            }
            else if (d + e == 0)
            {
                flagSum = true;
            }

            Console.WriteLine("Do we have sum with 0? - {0}", flagSum);
        }
    }
}