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: [84.527, 159.538, -20.208, 42.181, -12.587, -86.549, 131.349, 63.615, 150.304]
Example Output: 56.908

Example Input: [127.703, -82.203, 53.438]
Example Output: 32.979

Example Input: [2.927, -48.169, 10.598]
Example Output:
-11.548