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: [169.737, 56.872, 102.557, -9.77]
Example Output: 79.849

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

Example Input: [239.856, 55.271, -85.733, 237.012, -58.101, 214.516, 107.481, 156.275]
Example Output:
108.322