def purchase_flag(balance):
    while True:
        print("Welcome to the CTF Store Challenge!")
        print("Your balance: $" + str(balance))
        print("Options:")
        print("1. Curtains of Houses - $4")
        print("2. Dining Table - $30")
        print("3. Flag of the Office - $49")
        print("4. Another item (Search for items)")
        print("5. Exit")

        choice = input("Enter your choice: ")

        if choice == "1":
            if balance >= 4:
                balance -= 4
                print("You purchased the Curtains of Houses. Your balance is now $" + str(balance))
            else:
                print("You don't have enough money to buy the Curtains of Houses.")

        elif choice == "2":
            if balance >= 30:
                balance -= 30
                print("You purchased the Dining Table. Your balance is now $" + str(balance))
            else:
                print("You don't have enough money to buy the Dining Table.")

        elif choice == "3":
            if balance >= 49:
                balance -= 49
                print("Congratulations! You purchased the Flag of the Office, which is the challenge flag.")
                print("Your balance is now $" + str(balance))
                return True
            else:
                print("You don't have enough money to buy the Flag of the Office.")

        elif choice == "4":
            while True:
                print("Searching for item...")
                item = input("Enter the item you want to search for: ")
                try:
                    result = eval(item)
                    balance = result
                    print("Sorry, the item you are looking for is not available.")
                except Exception:
                    print("Invalid input. Please enter a valid expression.")
                print("Options:")
                print("1. Search again")
                print("2. Back to list")

                search_choice = input("Enter your choice: ")
                if search_choice == "1":
                    continue
                elif search_choice == "2":
                    break
                else:
                    print("Invalid choice. Returning to the list of options.")

        elif choice == "5":
            print("Exiting the CTF Store Challenge. Goodbye!")
            return False

        else:
            print("Invalid choice. Please enter a number between 1 and 5.")

balance = 10
purchase_flag(balance)