I put on my extra jacket, my scarf, my gloves and my skullcap as I headed out of the house today. It was actually semi-decent outside, with 47 °F /8 °C.
At the Capitol Hill train station, I put my mask on as well. A severe flu season is underway here in the US.
At the second-hand book store in U-district, I bought a book about the greatest unsolved problem in mathematics: The Riemann Hypothesis.