--description--

Oregon license plates consist of three letters followed by a three digit number (each digit can be from [0...9]).

While driving to work Seth plays the following game:

Whenever the numbers of two license plates seen on his trip add to 1000 that's a win.

E.g. MIC-012 and HAN-988 is a win and RYU-500 and SET-500 too (as long as he sees them in the same trip).

Find the expected number of plates he needs to see for a win. Give your answer rounded to 8 decimal places behind the decimal point.

Note: We assume that each license plate seen is equally likely to have any three digit number on it.

--hints--

licensePlates() should return 40.66368097.

assert.strictEqual(licensePlates(), 40.66368097);

--seed--

--seed-contents--

function licensePlates() {

  return true;
}

licensePlates();

--solutions--

// solution required