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: [148.261, -51.308, -98.748, -41.832, 44.313, -41.042, -19.943]
Example Output: -8.614

Example Input: [82.439, -85.167, 100.665, -83.297]
Example Output: 3.66

Example Input: [116.81, 174.26, 214.05]
Example Output:
168.373