using System;
using System.Linq;
using System.Collections.Generic;
using System.IO;
 
public class Test
{
 
	public static void Main()
	{
        var listDegree = new[] { 1, 4, 5, 6 };
 
        var totalCosts = listDegree
            .Select((num,index) => new{num,index})
            .GroupBy(x => x.index / 2)
            .Select(g => g.Sum(x => x.num));
 
        foreach(var totalCost in totalCosts)
            Console.WriteLine(totalCost);
	}
}

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