What is the capital letter of Beijing?

The Ling Fei Classic has 43 lines, each page is 20.8 × 8.9cm, which is of course average. In fact, the length and width of each page are not uniform. For example, the first page is the largest, but the actual writing area is similar, with 5 columns per page and 17 words per column, with an average of1.23x1.8cm.