enrico, I'll see your
and raise you
Go back to the person who gave you the requirment and ask them how they would like to describe the "Grand" total.
I'd suggest "Useless figure which might be very big, or very small, but likely somewhere in the middle, in actual value depending on the currencies in the sub-totals above - sorry, add them up yourself if you are interested in the answer, here's mine" 1920.
Either do it in a "base" currency, or ditch it. It is absurd.