Use three colors of red, white and black to randomly dye each small rectangle in a 3*n rectangle with one color. When n is at least how much, can at least two columns be dyed in exactly the same way?
用红白黑三种颜色给一个3*n的长方形中的每一个小长方形随意染上一种颜色，n至少为多少时，才能保证至少有两列染色方式完全一样？
<gadget id="calculator">3 * 3 * 3</gadget>
<output>27</output>

<gadget id="calculator">27 + 1</gadget>
<output>28</output>

<result>28</result>