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

namespace _1020
{

    public class _1020
    {
        public static void Main(string[] args)
        {
            string stroka_vxod = Console.ReadLine();
            string[] strohki = stroka_vxod.Split(' ');
            int n = int.Parse(strohki[0]);
            double r = double.Parse(strohki[1]);
            double dov_nut = 0;
            dov_nut += Math.PI * 2 * r;
            double[,] d = new double[2, n];
            double x1, x2, y1, y2;
            for (int i = 0; i < n; i++)
            {
                string vxid_point = Console.ReadLine();
                string[] pointu = vxid_point.Split(' ');
                d[0, i] = double.Parse(pointu[0]);
                d[1, i] = double.Parse(pointu[1]);
                if (i > 0)
                {
                    x1 = d[0, i];
                    x2 = d[1, i];
                    y1 = d[0, i - 1];
                    y2 = d[1, i - 1];

                    double tum_sum = 0;

                    tum_sum = Math.Sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
                    dov_nut += tum_sum;


                }


            }
            double  x0 = d[0, 0];
            double y0 = d[1, 0];
            double xl = d[0, n - 1];
            double yl = d[1, n - 1];
            double last_sum = 0;
            last_sum = Math.Sqrt((xl - x0) * (xl - x0) + (yl - y0) * (yl - y0));
            dov_nut += last_sum;
            double final = double.Parse(dov_nut.ToString("F2"));
            Console.Write(final);

        }

    }

}



Thanks!