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: [80.113, -28.006, -40.254, 222.454, 29.784, 129.871, 141.71, -44.716, -22.74]
Example Output: 52.024

Example Input: [89.776, -37.895, -45.315, 75.805, 144.052, 150.156]
Example Output: 62.763

Example Input: [120.251, 240.944]
Example Output:
180.598