Given the task definition and input, reply with output. In this task, you will use your knowledge about language (and common sense) to determine what element the marked number refers to. The numbers are marked with two underlines around them, like: _ number _. Your answer should be chosen from the given text, and should not contain other words.

Humbert: How are the piano lessons going ?
Lolita: Fine . Great . Excellent . Wonderful . Perfect .
Humbert: Especially since you missed the last _ two _ .
lessons