public Pair Add(Pair p1, Pair p2)
        {
            Pair result =new Pair();
               result.First = p1.First + p2.First;
               result.Second = p1.Second + p2.Second;

            return result;
        }
        public Pair Substract(Pair p1, Pair p2)
        {
            Pair result=new Pair();

            result.First = p1.First - p2.First;
            result.Second = p1.Second - p2.Second;

            return result;
        }