You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(1S)-1-(1H-benzimidazol-2-yl)ethyl]-2-(1-methyl-2,4-dioxo-1,3-diazaspiro[4.5]decan-3-yl)acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H25N5O3
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