On a 10*10 checkerboard, how many squares can a straight line pass through?
在10*10的方格棋盘中，画一条直线最多可穿过多少个方格．
<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">10 + 9</gadget>
<output>19</output>

<result>19</result>