You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 2-[[2-[[2-[[2-amino-3-(1H-imidazol-5-yl)propanoyl]amino]-5-(diaminomethylideneamino)pentanoyl]amino]-3-sulfanylpropanoyl]amino]-3-hydroxypropanoic acid into molecular formula.
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C18H31N9O6S
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