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: [159.965, 172.082]
Example Output: 166.024

Example Input: [72.326, -74.6, 127.566, -54.848, 198.529, -44.061, -28.155]
Example Output: 28.108

Example Input: [58.407, -69.319, -54.848, -86.651, 18.009, 120.074, 160.505, 60.501, 121.406]
Example Output:
36.454