There are eight points A, B, C, D, E, F, G, and H on the circumference of the circle. A triangle can be made by connecting any 3 points. Among them, how many triangles can be made with C as a vertex.
圆周上有A、B、C、D、E、F、G、H八个点，任意3点连线，就可作出一个三角形，其中以C为一个顶点的三角形，能作出多少个．
<gadget id="calculator">6 + 5 + 4 + 3 + 2 + 1</gadget>
<output>21</output>

<result>21</result>