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: [2.81, 52.99, 55.279, 75.682, 73.835, 148.077, -54.162, 112.112]
Example Output: 58.328

Example Input: [45.965, 169.829, 169.201, 81.293, 7.549, 223.189, 220.534]
Example Output:
131.08