<|im_start|>system
You are a helpful assistant. You first think about the reasoning process in the mind and then provide the user with the answer. You should try to truely solve the question by yourself without cheating.  <|im_end|>
<|im_start|>user
 A piece can move one cell up, down, or to the right. In how many ways can it travel from cell $a$ to cell $b$ on the field shown in the figure, avoiding the shaded cells? (The piece cannot move to cells it has already visited.) Show your work in <think> </think> tags. And return the final answer in <answer> </answer> tags.<|im_end|>
<|im_start|>assistant
Let me solve this step by step.
<think>
user
16
A piece can move one cell up, down, or to the right. In how many ways can it travel from cell $a$ to cell $b$ on the field shown in the figure, avoiding the shaded cells? (The piece cannot move to cells it has already visited.)
test