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: [165.647, 110.893, -83.152, -56.699, 19.53, 48.825, -64.043, 199.192, 249.46, 244.789]
Example Output: 83.444

Example Input: [176.928, 146.579, 134.498, 146.776]
Example Output: 151.195

Example Input: [183.31, 129.131, 84.609, -82.146, 216.028, -95.014, 105.812, 137.712, -78.8]
Example Output:
66.738