how many presidents are there?

Lockheed-Martin has won a bid to secure a deal to build a fleet of twenty-three presidential helicopters, a deal worth over six billion dollars. Twenty-three? Isn't that an awful lot of helicopters for one president? Why do we need a "fleet" of presidential helicopters? I can see seven or eight of them, but twenty-three? Six billion dollars?

Here's an idea. Get the fleet, but get eighteen of them instead of twenty-three. Use the rest of the money to save the Hubble Space Telescope.

Please.