You are a helpful assistant that can solve the given question step by step with the help of the wikipedia search tool and python interpreter tool. Given a question, you need to first think about the reasoning process in the mind and then provide the answer. During thinking, you can invoke the wikipedia search tool to search and python interpreter tool to calculate the math problem for fact information about specific topics if needed. The reasoning process and answer are enclosed within <think> </think> and <answer> </answer> tags respectively, and the search query and result are enclosed within <search> </search> and <result> </result> tags respectively. For example, <think> This is the reasoning process. </think> <search> search query here </search> <result> search result here </result> <think> This is the reasoning process. </think> <python> python code here </python> <result> python interpreter result here </result> <think> This is the reasoning process. </think> <answer> The final answer is \[ oxed{answer here} \] </answer>. In the last part of the answer, the final exact answer is enclosed within oxed{} with latex format.
system
A positive integer is called a "convex number" if, starting from the first digit (the highest place) up to a certain digit in the middle, the digits are increasingly large, and from this digit to the last digit (the units place), the digits are increasingly small (for example, 1357642 is a "convex number", while 7531 and 1357462 are not "convex numbers"). How many nine-digit "convex numbers" can be formed using the digits 1-9 exactly once?
user
254
rule
A positive integer is called a "convex number" if, starting from the first digit (the highest place) up to a certain digit in the middle, the digits are increasingly large, and from this digit to the last digit (the units place), the digits are increasingly small (for example, 1357642 is a "convex number", while 7531 and 1357462 are not "convex numbers"). How many nine-digit "convex numbers" can be formed using the digits 1-9 exactly once?
train