Zdrавейте! Ако може някой да ми обясни защо получавам тази грешка.

Условие: https://softuni.bg/downloads/svn/soft-tech/Sept-2017/Programming-Fundamentals-Extended-November-2017/04.%20Programming-Fundamentals-Extended-Dictionaries-and-LINQ/04.%20Programming-Fundamentals-Extended-Dictionaries-and-LINQ-Lab.docx   // Задача 02.

Мое решение: с дадените примери получавам коректен резултат, включително и с форматирането.

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

namespace Lab
{
    class Program
    {
        static void Main(string[] args)
        {
            Average_Sudents_Grade();
        }

        private static void Average_Sudents_Grade()
        {
            var n = int.Parse(Console.ReadLine());
            Dictionary<string, List<double>> students = new Dictionary<string, List<double>>();
            for (int i = 0; i < n; i++)
            {
                string[] info = Console.ReadLine().Split(" ").ToArray();
                string name = info[0];
                double grade = double.Parse(info[1]);
                //
                if (!students.ContainsKey(name))
                {
                    List<double> temp = new List<double>();
                    temp.Add(grade);
                    students.Add(name, temp);
                }
                else
                {
                    students[name].Add(grade);
                }
            }
            foreach (var pair in students)
            {
                Console.Write($"{pair.Key} ->");
                foreach (var item in pair.Value)
                {
                    Console.Write($" {item:f2}");
                }
                Console.WriteLine($" (avg: {pair.Value.Average():F2})");
            }
        }

        private static void P01()
        {
            string[] sequenc = Console.ReadLine().ToLower().Split(' ').ToArray();
            var dict = new Dictionary<string, int>();
            //
            foreach (var word in sequenc)
            {
                if (!dict.ContainsKey(word))
                {
                    dict.Add(word, 1);
                }
                else
                {
                    dict[word]++;
                }
            }
            List<string> str = new List<string>();
            foreach (var pair in dict)
            {
                if (pair.Value % 2 != 0)
                {
                    str.Add(pair.Key);
                }
            }
            Console.WriteLine(string.Join(", ", str));
        }
    }
}