human
Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
In a classroom, there are four students: Alice, Bob, Charlie, and David. The teacher gives each student a different colored envelope containing a secret message. Alice gets a green envelope, Bob gets a blue one, Charlie receives a purple one, and David is given an orange envelope. During recess, Alice switches her green envelope with Bob's blue one without him knowing. Meanwhile, Charlie accidentally drops his purple envelope, and David picks it up, thinking it's his own. After recess, the teacher asks the students to open their envelopes and read the messages aloud. What color envelope does each student think they have?

Respond very briefly.

### Response:
gpt
Alice now thinks she has a blue envelope because she secretly switched her green one with Bob's blue one. Bob believes he has a green envelope, as he is not aware that Alice switched her green one with his blue one. Charlie thinks he has lost his envelope since he accidentally dropped it, and David thinks he has a purple envelope because he picked up Charlie's dropped purple one, mistaking it for his own orange envelope.