class Program
    {
        static void Shuttle(double[,] arr)
        {
            List<double> P = new List<double>();
            List<double> A = new List<double>();
            List<double> Q = new List<double>();
            P.Add(arr[0, 0]);
            A.Add(-arr[0, 1] / P[0]);
            Q.Add(arr[0,arr.GetLength(0)] / P[0]);
            /////////////////////////////////////////////
            int j = 0;//под главной
            for(int i = 1; i < arr.GetLength(0); i++)
            {
                int m = i + 1;//над главной
                P.Add(arr[i, i] + arr[i, j] * A[j]);
                A.Add(-arr[i, m] / P[i]);
                Q.Add((arr[i, arr.GetLength(0)] - arr[i, j] * Q[j]) / P[i]);
                j++;
            }
            A.Remove(A[A.Count-1]);
            /////////////////////////////////////////////
            List<double> X = new List<double>(arr.GetLength(1)-1);
            X.Add(Q[Q.Count - 1]);
            Console.WriteLine("X[" + Q.Count + "]=" + X[0]);
            int jj = 0;
            for(int i = A.Count; i > 0; i--)
            {
                X.Add(A[i-1] * X[jj] + Q[i-1]);
                jj++;
                Console.WriteLine("X[" + i + "]=" + X[jj]);
            }
        }

        public static void Main()
        {
            double[,] array = new double[,] { { 2, -1, 0, 0, 0, -25 }, { -3, 8, -1, 0, 0, 72 },
                { 0, -5, 12, 2, 0, -69 },{ 0, 0, -6, 18, -4, -156 },{0,0,0,-5,10,20 } };
            for(int i = 0; i < array.GetLength(0); i++)
            {
                for(int j = 0; j < array.GetLength(1); j++)
                {
                    Console.Write(array[i, j] + "");
                    Console.Write("|");
                }
                Console.WriteLine();
            }
            Console.WriteLine();
            Shuttle(array);
        }
    }