There are 2 roads from A to B, 3 roads from B to C, and 3 roads from C to D. Now Xiaoming wants to go from A to D through B and C. How many different ways to go.
从甲地到乙地有2条路，从乙地到丙地有3条路，从丙地到丁地有3条路，现在小明要从甲地经乙、丙两地到丁地，共有多少种不同的走法．
<gadget id="calculator">2 * 3 * 3</gadget>
<output>18</output>

<result>18</result>