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: [159.243, 17.964, 13.543, 175.402, -52.441, -34.741, 158.461]
Example Output: 62.49

Example Input: [21.659, 63.646, -97.361]
Example Output: -4.019

Example Input: [73.791, 15.601, 82.396, 238.285]
Example Output:
102.518