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: [-31.252, 246.934, 96.512, 19.356, -50.759, 134.528, 176.914, 17.007, 171.802]
Example Output: 86.782

Example Input: [235.595, 227.906, -52.328, 100.922, 124.177, 149.582, -41.738]
Example Output: 106.302

Example Input: [40.735, 180.126, 212.447]
Example Output:
144.436