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: [219.769, -36.26, 3.121, -22.5, 124.372]
Example Output: 57.7

Example Input: [24.119, 239.006, 239.873, 236.27, 134.34]
Example Output: 174.722

Example Input: [161.155, 137.077, 34.815, 115.989]
Example Output:
112.259