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: [216.087, 41.07, 213.683, 53.822, 31.214]
Example Output: 111.175

Example Input: [70.496, 183.122, 75.017, -19.287, 53.364, -12.389, 249.47, -88.484, 249.98, 35.226]
Example Output: 79.652

Example Input: [5.771, 202.329, 96.66, 104.638, 235.193]
Example Output:
128.918