Fill in the blank (_) in the following sentence from the following choices.
Sentence: The toothpaste of Robert works better than that of Joel, so _ must use a name brand toothpaste.

Choice 1: The toothpaste of Robert works better than that of Joel, so Robert must use a name brand toothpaste.
Choice 2: The toothpaste of Robert works better than that of Joel, so Joel must use a name brand toothpaste.
Which of the choices is correct? Respond with only "1" or "2" and no additional text.
1
2.