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: [138.63, 106.759, 86.625]
Example Output: 110.671

Example Input: [227.601, -61.961, 78.822, -29.52, 126.039, -44.098, 112.374, -19.23, 69.758]
Example Output: 51.087

Example Input: [12.999, 219.01, -2.502]
Example Output:
76.502

