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: [141.597, -13.558, -15.987, -52.44, 77.914]
Example Output: 27.505

Example Input: [159.381, -84.046]
Example Output: 37.668

Example Input: [129.86, -74.992, 143.161]
Example Output:
66.01