You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule 2-(3-fluorophenyl)-N-[[6-(4-methoxyphenyl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl]methyl]acetamide .
user
C21H18FN5O2
assistant