Методы вычислений (лагранжа)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Lagranzh
{
    class Program
    {
        static double funct(double xi)
        {
            return xi * xi * xi / 4;
        }

        static void Main(string[] args)
        {
            double y;
            double sum = 0;
            double pr = 1;

            Console.WriteLine("Please, enter number of intermediate values");
            int n = int.Parse(Console.ReadLine());

            List<double> ixi = new List<double>();

            for(int i=0;i<n;i++)
            {
                Console.WriteLine("Enter {0} intermediate value", i);
                double iks = Convert.ToDouble(Console.ReadLine());
                ixi.Add(iks);
            }

            Console.WriteLine("Please enter the x = ");
            double x = double.Parse(Console.ReadLine());


            for (int i=0;i<ixi.Count;i++)
            {
                y = funct(ixi[i]);
                for (int j=0;j<n;j++)
                {
                    if (i != j)
                    {
                        pr *= (x - ixi[j]) / (ixi[i] - ixi[j]);
                    }
                }
                sum += y * pr;
                pr = 1;
            }
            Console.WriteLine();
            Console.WriteLine("{0}", sum);
        }
    }
}