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: [131.164, 99.999, 138.488, 57.264, -40.069, -82.402, -42.836]
Example Output: 37.373

Example Input: [-66.676, -7.063, -18.028, 13.407, 54.369, 148.394, -93.155]
Example Output: 4.464

Example Input: [65.591, -56.104, -28.389, -22.521]
Example Output:
-10.356