if you cut it into three pieces, it's easier to understand how to do it, as I show in the picture. when you are done splitting this into three parts you start multiplying. The side bases' digits are 31*23=713 and you need to do that twice, so 713+713=1,426. Next, you find the side-length for, and multiply, the middle base which is 23*19=437. Finally, you add all of that together 1,426+437=1,863.
