Vending machine

using System;

namespace Excercises_VendingMachine
{
    class Program
    {
        static void Main(string[] args)
        {
            string input = Console.ReadLine();
            double sum = 0;

            while (input != "Start")
            {
                double coin = double.Parse(input);

                if (coin == 0.1 || coin == 0.2 || coin == 0.5 || coin == 1 || coin == 2)
                {
                    sum = sum + coin;
                }
                else
                {
                    Console.WriteLine($"Cannot accept {coin}");
                }

                input = Console.ReadLine();
            }

           string articul = Console.ReadLine();

            while (articul != "End")
            {

                if (articul == "Nuts")
                {
                    double price = 2;
                    if (sum - price >= 0)
                    {
                        Console.WriteLine($"Purchased nuts");
                        sum = sum - price;
                    }
                    else
                    {
                        Console.WriteLine($"Sorry, not enough money");
                    }
                }
                else if (articul == "Water")
                {
                    double price = 0.7;
                    if (sum - price >= 0)
                    {
                        Console.WriteLine($"Purchased water");
                        sum = sum - price;
                    }
                    else
                    {
                        Console.WriteLine($"Sorry, not enough money");
                    }
                }
                else if (articul == "Crisps")
                {
                    double price = 1.5;
                    if (sum - price >= 0)
                    {
                        Console.WriteLine($"Purchased crisps");
                        sum = sum - price;
                    }
                    else
                    {
                        Console.WriteLine($"Sorry, not enough money");
                    }
                }
                else if (articul == "Soda")
                {
                    double price = 0.8;
                    if (sum - price >= 0)
                    {
                        Console.WriteLine($"Purchased soda");
                        sum = sum - price;
                    }
                    else
                    {
                        Console.WriteLine($"Sorry, not enough money");
                    }
                }
                else if (articul == "Coke")
                {
                    double price = 1;
                    if (sum - price >= 0)
                    {
                        Console.WriteLine($"Purchased coke");
                        sum = sum - price;
                    }
                    else
                    {
                        Console.WriteLine($"Sorry, not enough money");
                    }
                }
                else
                {
                    Console.WriteLine("Invalid