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: [161.683, 162.041, 187.429, -79.681, 60.809, 225.806]
Example Output: 119.681

Example Input: [138.63, 106.759, 86.625]
Example Output: 110.671

Example Input: [50.724, -76.389, 149.544, 208.956, 224.667, 164.107, 223.808, 22.124, 89.233]
Example Output:
117.419