Can anyone help me?
This is my code wich has Crash on the 4th test:
using System;
using System.Diagnostics;
using System.Runtime.CompilerServices;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Globalization;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            System.Threading.Thread.CurrentThread.CurrentCulture = CultureInfo.InvariantCulture;
            NumberFormatInfo nfi = NumberFormatInfo.InvariantInfo;
            String[] str = Console.ReadLine().Split(new char[] { ' ', '\n', '\t' }, StringSplitOptions.RemoveEmptyEntries);
            int n = int.Parse(str[0], nfi);
            int r = int.Parse(str[1], nfi);
            double length = 0;

            if (n == 1)
            {
                length += r * Math.PI * 2;
                Console.Write(String.Format(nfi, "{0:F2}", length));
                return;
            }
            double[][] mat = new double[n][];
            for (int i = 0; i < n; i++)
                mat[i] = new double[2];

            for (int i = 0; i < n; i++)
            {
                String[] str1 = Console.ReadLine().Split(new char[] { ' ', '\n', '\t' }, StringSplitOptions.RemoveEmptyEntries);
                mat[i][0] = Double.Parse(str1[0], nfi);
                mat[i][1] = Double.Parse(str1[1], nfi);
            }

            for (int i = 0; i < n; i++)
            {
                if (i == n - 1)
                {
                    length += Math.Sqrt((mat[i][0] - mat[0][0]) * (mat[i][0] - mat[0][0]) + (mat[i][1] - mat[0][1]) * (mat[i][1] - mat[0][1]));
                    break;
                }
                length += Math.Sqrt((mat[i][0] - mat[i + 1][0]) * (mat[i][0] - mat[i + 1][0]) + (mat[i][1] - mat[i + 1][1]) * (mat[i][1] - mat[i + 1][1]));
            }
            length += r * Math.PI * 2;

            Console.Write(String.Format(nfi, "{0:F2}", length));
        }
    }
}