You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-[[2-[4-(4-carbamimidoylphenyl)-2,3-dioxopiperazin-1-yl]acetyl]amino]-3-pyridin-2-ylpropanoic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H22N6O5
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