using System;

public class Program

{

    public static bool CheckKvasChange(int[] bills) 

    {

        int len = bills.Length;

        int five = 0,

            ten = 0;

​

        for (int i = 0; i < len; i++)

        {

            switch (bills[i]) 

            {

                case 5:

                    five += 1;    

                    break;

                case 10:

                    if (five == 0) return false;

                    five -= 1;

                    ten += 1;

                    break;

                default: 

                    if (ten > 0 && five > 0) {

                        ten -= 1;

                        five -= 1;

                    }

                    else if (five >= 3)

                        five -= 3;

                    else

                        return false;

                    break;

            }

        }

​

        return true;

    }

    public static void Main()

    {

        Console.WriteLine("UniLecs");

        // tests

        Console.WriteLine(CheckKvasChange(new int[] { 5, 5, 5, 10, 20 }).ToString());  // true

        Console.WriteLine(CheckKvasChange(new int[] { 5, 5, 10, 10, 20 }).ToString()); // false

    }

}