In a triangle, the length of the first side is 6 cm, the length of the second side is 7 cm, and the length of the third side must be less than how many cm.
在三角形中，第一条边长是6厘米，第二条边长是7厘米，第三条边长一定小于多少厘米．
<gadget id="calculator">7 + 6</gadget>
<output>13</output>

<result>13</result>