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: [82.748, 43.804, -13.469, 226.705, -7.478]
Example Output: 66.462

Example Input: [153.482, 150.917]
Example Output: 152.2

Example Input: [-26.632, -55.927, 227.255, 237.568, 203.07, 200.797, 31.871]
Example Output:
116.857