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: [73.331, 85.459, 59.798, -35.019]
Example Output: 45.892

Example Input: [160.713, 125.985, 186.982, -94.178, 183.77]
Example Output: 112.654

Example Input: [-74.318, 134.526, 111.234, 221.516, 216.098, 46.965, 20.36, -84.978, 194.799]
Example Output:
87.356