A rectangle is 20 centimeters long and 15 centimeters wide. Now it is necessary to put black dots on its four corners and sides so that the distance between every two adjacent black dots is equal. How many dots can be dotted at least.
一个长方形，长20厘米，宽15厘米，现在要在它的四个角上和边上点上黑点，使每相邻的两个黑点间的距离相等，最少能点多少个点．
<gadget id="calculator">20 + 15</gadget>
<output>35</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">35 * (2/5)</gadget>
<output>14</output>

<result>14</result>