I'll be serious. This is what Boeing says:
Flight Management System The flight management system (FMS) is comprised of the following components:
• flight management computer system (FMCS)
• autopilot/flight director system (AFDS)
• autothrottle (A/T)
• inertial reference systems (IRS)
• global positioning system (GPS).
So since IRS and GPS are subcomponents of the FMS, I would say the answer is: FMS