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: [245.271, 40.965, 133.913, 212.104]
Example Output: 158.063

Example Input: [217.523, 92.701, -55.65, -89.359, 55.742, 158.634, -31.883, 206.554]
Example Output: 69.283

Example Input: [-83.215, 70.308, -69.135]
Example Output:
-27.347