07.StudetsAcademy

using System;
using System.Collections.Generic;
using System.Linq;
class StudentsAcademy
{
    static void Main(string[] args)
    {
        Dictionary<string, double[]> inputDict = new Dictionary<string, double[]>();
        int num = int.Parse(Console.ReadLine());
        int count;
        for (int i = 0; i < num; i++)
        {

            string input = Console.ReadLine();
            double grade = double.Parse(Console.ReadLine());

            if (!inputDict.ContainsKey(input))
            {
                count = 1;
                inputDict.Add(input, new double[2] {grade, 1});
            }
            else
            {
                inputDict[input][1] += 1;
                inputDict[input][0] += grade;
            }

        }
        foreach (var item in inputDict)
        {
            inputDict[item.Key][0] /= inputDict[item.Key][1];
        }
        foreach (var kvp in inputDict.OrderByDescending(w => w.Value[0]))
        {

            if (kvp.Value[0] >= 4.50)
            {
                Console.WriteLine($"{kvp.Key} -> {kvp.Value[0]:f2}");
            }
        }
    }
}