You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-(4-fluorophenyl)-4-[(S)-(2-fluorophenyl)-[1-(2-methoxyethyl)tetrazol-5-yl]methyl]piperazin-4-ium is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H25F2N6O+
assistant