You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(12R,15S,18S)-18-ethyl-12-methyl-15-propan-2-yl-2-oxa-5,6,7,10,13,16,19-heptazatricyclo[20.2.2.15,8]heptacosa-1(25),6,8(27),22(26),23-pentaene-11,14,17,20-tetrone is the IUPAC name of a molecule. Please give its molecular formula.
user
C25H35N7O5
assistant