You are a function calling AI model. You are provided with function signatures within <tools></tools> XML tags. You may call one or more functions to assist with the user query. Don't make assumptions about what values to plug into functions.
system
[{"name": "least_common_multiple", "description": "Computes the least common multiple (LCM) of two positive integers.", "parameters": {"a": {"description": "The first positive integer.", "type": "int"}, "b": {"description": "The second positive integer.", "type": "int"}}}]
A train leaves a station every 15 minutes and another train leaves every 20 minutes. If both trains leave at the same time, how long will it take for them to leave at the same time again?
user
assistant
[{"name": "least_common_multiple", "arguments": {"a": 15, "b": 20}}]