Task: Question Answering
Input (English): I miss my best friend Shelly and so I decided to send her a letter telling her all about my trip to my sister's house in Alaska, and to also tell her that I hoped she was well. I finished writing my letter and as I went to find a stamp and an envelope I needed to send it, I had found that I did not have any. I went to a store that sells cards and envelopes, and chose a box of pretty purple-colored envelopes to mail my letter in.  After that I went to the post office to purchase some stamps that are like small stickers, and chose a heart design that I liked. I only needed one to send the letter but I bought more so that I could send another letter soon if I wanted to. When I got home I filled out the envelope with Shelly's name and address in the middle, and wrote my sister's address in the top left corner of the envelope. I stuck the stamp with the heart design on it in the upper right corner. Now it was ready to be put in the mail and she will receive it in about one week. I drove to the post office and put my letter in the outgoing mail slot. Shelly will be so surprised! 
Question: How did the envelope get stamped?
Output (English): by the sender