Практика 2, задание 1, номер 11

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

namespace mainSolution
{
    public class MyException : Exception
    {
        public MyException(string messege) : base(message: messege + "\n\n\n Exception founded by Decibit\n\n\n") { }
        public MyException() : base()
        {

        }
        public void Messsage()
        {
            Console.WriteLine("\n\n\n\n\n\n Invalid number, please enter a number from 1 to 10 \n\n\n\n\n\n");
        }


    }
    class Input
    {
        private static IEnumerator<string> getin()
        {
            while (true)
                foreach (string s in Console.ReadLine().Split().Where(x => x.Length > 0))
                    yield return s;
        }

        private IEnumerator<string> inp = getin();

        public string GetString() { inp.MoveNext(); return inp.Current; }
        public int GetInt() { return int.Parse(GetString()); }
        public long GetLong() { return long.Parse(GetString()); }
        public double GetDouble() { return double.Parse(GetString()); }
    }

    static class Program
    {
        static double sqr(double a) => a * a;
        static double length(double x1, double y1, double x2, double y2) => Math.Sqrt(sqr(x1 - x2) + sqr(y1 + y2));

        static int next(int i) => (i + 1)%3;

        static void Main(string[] args)
        {

            double[] x = new double[3];
            double[] y = new double[3];
            Input cin = new Input();
            for (int i = 0; i < 3; i++)
            {
                x[i] = cin.GetDouble();
                y[i] = cin.GetDouble();
            }
            double ans = 0;
            for (int i = 0; i < 3; i++)
            {
                ans += length(x[i], y[i], x[next(i)], y[next(i)]);
            }
            Console.WriteLine(ans);
        }
    }

}