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: [84.091, 17.564, 58.169, 6.482, 53.256, 216.444, 171.489]
Example Output: 86.785

Example Input: [199.974, 2.205, 197.996, 172.426, 182.153, 42.045, 53.238, 18.021, 83.903]
Example Output: 105.773

Example Input: [-64.444, 127.032, 230.129, 118.938, 74.084, 147.077, -79.149, -99.452, 22.993]
Example Output:
53.023