using System;

using System.Threading;

using System.Collections.Generic;

​

class Wallet

{

    private decimal balance = 0;

    private readonly object lockObject = new object();

    private List<string> transactionLogs = new List<string>();

​

    public void TopUp(decimal amount)

    {

        balance += amount;

        transactionLogs.Add($"Top-up: {amount} at {DateTime.Now}");

    }

​

    public decimal GetBalance()

    {

        return balance;

    }

​

    public void DisplayTransactionLogs()

    {

        foreach (var log in transactionLogs)

        {

            Console.WriteLine(log);

        }

    }

}

​

class Program

{

    static void Main()

    {

        Wallet wallet = new Wallet();

​

        Thread[] threads = new Thread[10];

        for (int i = 0; i < 10; i++)

        {

            threads[i] = new Thread(() => wallet.TopUp(100));

            threads[i].Start();

        }

​

        foreach (var thread in threads)

        {

            thread.Join();

        }

​

        Console.WriteLine("Final balance: " + wallet.GetBalance());

        wallet.DisplayTransactionLogs();

    }

}

​