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: [54.715, 180.963, 239.308, 175.084, 147.044, 136.262, 184.009]
Example Output: 159.626

Example Input: [149.806, 232.621, 119.06]
Example Output: 167.162

Example Input: [-62.174, 175.981, -24.953, -88.989, -30.185, -43.212, 21.367]
Example Output:
-7.452