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: [87.258, 29.558, -48.199, -28.615, 46.642]
Example Output: 17.329

Example Input: [-51.709, 7.971, 56.819, 147.653, 82.016, 33.283, 17.84, -45.317, 152.854, 6.908]
Example Output: 40.832

Example Input: [119.585, 235.292, 121.008, -36.186]
Example Output:
109.925