3. YiYi lives near Huashi, and she plans to ride a shared bike to the park. From Huashi station to the park, there are 3 stations in between, and each station has yellow, orange, red, and green shared bikes. If YiYi does not want to ride the same color bike at adjacent stations, then the total number of bike riding strategies for YiYi from home to the park is $\qquad$.
3. 【Answer】108