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: [-98.163, -66.763, 149.544, -89.893, -10.155]
Example Output: -23.086

Example Input: [-65.295, 113.842, -82.683, 235.996, 143.686, 31.127, 135.386, 217.657, -87.331]
Example Output: 71.376

Example Input: [120.461, 212.59, 146.876, 43.064, 9.191]
Example Output:
106.436