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: [229.461, -89.251, 170.954]
Example Output: 103.721

Example Input: [128.472, 149.361, 71.023, -96.651]
Example Output: 63.051

Example Input: [-23.355, 88.318, 246.788, 95.4, 224.777, 204.856, 41.596]
Example Output:
125.483