using System;

namespace _1020
{

    class Class1
    {

        [STAThread]
        static void Main(string[] args)
        {
            string s = Console.ReadLine();
            s = s.Replace('.',',');
            string[] w = s.Split(' ');
            int n = int.Parse(w[0]);
            double r = double.Parse(w[1]);
            double[,] k = new double[n,2];
            for(int i = 0; i < n; i++)
            {
                string s1 = Console.ReadLine();
                s1 = s1.Replace('.',',');
                string[] w1 = s1.Split(' ');
                k[i,0] = double.Parse(w1[0]);
                k[i,1] = double.Parse(w1[1]);
            }
            double sum = 0;
            for(int i = 0; i < n - 1; i++)
                sum += Math.Sqrt((k[i,0] - k[i + 1,0])*(k[i,0] - k[i + 1,0]) + (k[i,1] - k[i + 1,1])*(k[i,1] - k[i + 1,1]));
            sum += Math.Sqrt((k[0,0] - k[n - 1,0])*(k[0,0] - k[n - 1,0]) + (k[0,1] - k[n - 1,1])*(k[0,1] - k[n - 1,1]));
            sum += 2*Math.PI*r;
            sum += 0.005;
            string h = sum.ToString();
            h = h.Replace(',','.');
            int x = h.IndexOf('.');
            h = h.Insert(x+3, "r");
            string[] v = h.Split('r');
            Console.WriteLine(v[0]);
        }
    }
}