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: [-34.026, 86.773, 149.194, 228.14]
Example Output: 107.52

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

Example Input: [-84.662, -43.609, 92.367, 245.742, 129.135, 238.401, 234.962, 246.221]
Example Output:
132.32