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: [151.151, 144.049, 217.252]
Example Output: 170.817

Example Input: [218.46, 7.937, 155.624, 82.813, 93.516]
Example Output: 111.67

Example Input: [5.614, 16.139, -58.06]
Example Output:
-12.102