C50

When Doon came back, he did not know; for when Doon came back, she gloriously went to tea and chat with Mister Zhou.

When did Doon leave? I'm sorry, but Ding Mi still doesn't know. Because, when Doon left, she was dragged away by Mr Zhou to play chess.

All in all, Ding Duo didn't know when the protagonist, Dong, had come back or when he had left, but she knew that the protagonist had come back