Three line segments form a triangle, and two sides are 21 cm and 16 cm respectively, so what is the minimum centimeter of the third side (the length of a side is an integer number of centimeters).
三条线段组成一个三角形，有两条边分别是21厘米、16厘米，那么第三条边至少是多少厘米(边长是整厘米数)．
<result>6</result>