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: [-36.318, 176.066, 36.435, 132.732, -15.887, -24.851, 169.963, -98.796, 38.818]
Example Output: 42.018

Example Input: [122.544, 131.643, -43.903]
Example Output:
70.095