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-amino-9-[(1R,6S,8S,9S,10S,15S,17S,18S)-8-(2-amino-6-oxo-1H-purin-9-yl)-9,18-difluoro-3,12-dihydroxy-3,12-dioxo-2,4,7,11,13,16-hexaoxa-3lambda5,12lambda5-diphosphatricyclo[13.2.1.06,10]octadecan-17-yl]-1H-purin-6-one into molecular formula.
user
C20H22F2N10O12P2
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