Untitled

  static void Main(String[] args)
    {
        List<int> list2 = new List<int>() { 422346306, 940894801, 696810740, 862741861, 85835055, 313720373 };
        int k = 9;

        var z = nonDivisibleSubset(k, list2);
    }
 
 public static int nonDivisibleSubset(int k, List<int> s)
    {
        var x = GetPerm(s);


        var y = x.Where(x => x.Value % k != 0).Select(x=>x.Key).ToList();
        var a = y.SelectMany(x => x).ToHashSet();

        return a.Count();

    }

    static Dictionary<List<int>,int> GetPerm (List<int> list)
    {
        Dictionary<List<int>,int> perm = new Dictionary<List<int>, int>();

        for (int i = 0; i < list.Count; i++)
        {
            for (int j = i+1; j < list.Count; j++)
            {
                List<int> sumCouple = new List<int>();
                sumCouple.Add(list[i]);
                sumCouple.Add(list[j]);
                perm.Add(sumCouple, sumCouple.Sum());
            }

        }
        return perm;
    }