Choice 1

        print()
        customername = input("Enter the customer name: ")

        if customername not in CustomerNames:
            petname = input("Enter the pet's name:")
            customerid = len(CustomerNumbers) + CustomerNumbers[-1]
            PetNames.append(petname)
            CheckInTime.append("MM/DD/YYYY")
            CustomerNames.append(customername)
            CustomerNumbers.append(customerid)
            Duration.append(0)
            print()
            print()
            print("New customer successfully registered!\n")
            print(f'{"Customer Name":<24}{"ID":>6}')
            print("-" * 30)
            print (f'{customername: <24}{customerid:>6}')
            print()
        else:
            print()
            print("\nError. Customer is already registered.\n")