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: [-81.432, -63.059, 150.144, 55.203, 215.405, -89.797, 72.946]
Example Output: 37.059

Example Input: [26.145, -44.254, 127.581, 162.122, 82.003, 143.809, 96.47, 34.362, 71.469]
Example Output: 77.745

Example Input: [241.388, -37.843, -41.309, 26.588, 138.961, 235.54, -27.509]
Example Output:
76.545