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: [220.903, 155.959]
Example Output: 188.431

Example Input: [162.434, 99.656, 86.665, 13.03, 99.225, 43.608, -41.822, 206.671]
Example Output: 83.683

Example Input: [147.419, 150.879, -2.288, 131.631]
Example Output:
106.91