$4901$
16. Lego Explorer Guguji arrives at a medieval kingdom, which is ruled by an evil wizard. With the help of Guguji and his friends, the prince defeats the wizard and returns to his castle. The castle is built with many cubes with an edge length of 1 meter, arranged from top to bottom in a pattern as shown in the figure. The castle has a total of 25 layers. What is the surface area of the castle in square meters (excluding the bottom base area)?