using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        int[] input = new int[] { 1, 2, 3, 4, 5 };

        var result = input.SelectMany(x => input, (x,y) => new { x,y }).GroupBy(x => x.x + x.y);

        Console.WriteLine(string.Join("\n", result.Select(x => x.Key + ":" + string.Join(",",x.Select(y => $"({y.x},{y.y})")))));

    }

}