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: [125.987, 140.164, 103.07, -78.923, -92.734, -96.888]
Example Output: 16.779

Example Input: [-84.771, 60.727, 165.566, 27.782, 159.929, 167.451, -64.15]
Example Output: 61.791

Example Input: [58.026, 115.969, 145.375, 150.742, -55.764, 149.883, 167.287, -36.648, 87.587, -59.57]
Example Output:
72.289