The Go board is composed of 19 horizontal and vertical line segments, how many rectangles are formed by these line segments? (excluding squares).
围棋盘是由横、竖各19条线段构成的，则这些线段构成长方形的个数为多少．(不包括正方形)．
<gadget id="calculator">19 * 18</gadget>
<output>342</output>

<gadget id="calculator">342 / 2</gadget>
<output>171</output>

<gadget id="calculator">171 * 171</gadget>
<output>29_241</output>

<gadget id="calculator">29_241 - 2_109</gadget>
<output>27_132</output>

<result>27_132</result>