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: [-18.796, 194.818]
Example Output: 88.011

Example Input: [-10.287, -0.47, 195.152, 209.845, -64.645, -82.959, 106.327]
Example Output: 50.423

Example Input: [-67.913, -12.576, 195.616, 56.941, 175.886, -71.114, 17.551, 138.312, 45.143, 242.153]
Example Output:
72.0