12. A little ant lives in a rectangular cave (as shown in the figure, the lines represent paths). It crawls from point $A$ to point $B$, then to point $C$, and finally to point $D$, covering a total of 22 cm; It crawls from point $A$ to point $D$, then to point $C$, and finally to point $B$, covering a total of 29 cm; It crawls from point $A$ to point $B$, then to point $C$, and finally back to point $A$, covering a total of 30 cm. If the little ant starts from point $A$, crawls along every path in the cave, and finally arrives at point $C$, then it has crawled at least $\qquad$ cm.
【Analysis】$A B, C D$ are 5 cm long, $B C, A D$ are 12 cm long, $A C$ is 13 cm long; the route is $A \rightarrow B \rightarrow C \rightarrow A \rightarrow D \rightarrow C$, the total length is 47 cm