Complete the letter with at, of, in or on.

Dear Lucy,
Mary and I can canoe now! At last! So we’re very proud ... ourselves. Canoeing is a great sport, especially in a river full of rocks! Of course, we are not very good ... it yet, and at first we were really bad ... it. We fell into the river at least ten times, I’m sure ... that. I’m not afraid ... the river, but I’m not keen ... very cold water! Getting into the canoe was rather difficult too, but we’re quite quick ... that now. So we’re enjoying ourselves, but we’re rather tired ... the rain here. It’s been raining for three days.
Please write. I’ll be interested ... your news.
All the best,
Judy