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: [166.967, 154.381, -19.741, 157.124]
Example Output: 114.683

Example Input: [176.017, -45.57]
Example Output: 65.224

Example Input: [185.956, 96.71, 59.807, 103.782, 130.001, 65.209, -39.276, 220.618, 7.291, 40.978]
Example Output:
87.108