Pick up the biggest interrupt signal from a rectangular menu, and the rest is 12 cm wide.
As shown in the figure, (12-8) × 2+8× 2 = 4× 2+8× 2 = 8+16 = 24 (cm); The rectangle is12cm long and 8cm wide. After cutting the largest square from one end, what remains is a rectangle with a circumference of 24 cm. So the answer is: rectangle, 24.