In a triangle ABC, it is known that the lengths of the three sides are all integers in centimeters, and the lengths of the two sides are 5 cm and 8 cm respectively, and the length of the third side is at most how many centimeters.
在一个三角形ABC中，已知三条边的长度都是整厘米数，其中两边长分别是5厘米、8厘米，第三条边的长度至多是多少厘米．
<gadget id="calculator">8 + 5</gadget>
<output>13</output>

<gadget id="calculator">13 - 1</gadget>
<output>12</output>

<result>12</result>