using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public class Person 

    {

        public string Name;

        public double Age;

    }

    public static void Main()

    {

        string[] username = new string[0];

        string[] password = new string[0];

        int[] balance = new int[0];

        Array.Resize(ref username, username.Length + 1);

        username[username.Length - 1] = "test";

        Array.Resize(ref password, password.Length + 1);

        password[password.Length - 1] = "test1";

        Array.Resize(ref balance, balance.Length + 1);

        balance[balance.Length - 1] = 1000;

        Console.WriteLine($"{balance[0]}");

        int loggedIndex = 0;

        bool hasMatch = false;

        for(int i=0; i < username.Length; i++)

        {

            if(username[i] == "test" && password[i] == "test1")

            {

                hasMatch = true;

                loggedIndex = i;

                break;

            }

        }

        while(hasMatch)

        {

            balance[loggedIndex] = balance[loggedIndex] - 500;

            hasMatch = false;

        }

        Console.WriteLine($"{balance[0]}");

    }

}