In this task you will be given a list of numbers and you need to find the mean (average) of that list. The mean of a list can be found by summing every number in the list then dividing the result by the size of that list. The output should be rounded to 3 decimal places.

Example Input: [208.757, -63.857, 124.458, 25.069, -39.093, -85.924, 112.747]
Example Output: 40.308

Example Input: [209.13, -12.632, 247.489, 55.492, 8.967, -90.158, 193.743]
Example Output: 87.433

Example Input: [51.543, 232.919]
Example Output:
142.231