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: [-42.956, 89.597, -60.477, 101.972, 77.479]
Example Output: 33.123

Example Input: [-28.295, -24.828, -66.96, -12.108, -96.597, 110.99, 172.86, -18.752, 157.717]
Example Output: 21.559

Example Input: [97.857, -47.091, 77.519, 57.494, 119.734]
Example Output:
61.103