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: [-13.67, 239.672]
Example Output: 113.001

Example Input: [-67.542, 65.934, 223.305, 25.694, 159.037]
Example Output: 81.286

Example Input: [201.083, 203.145, 85.923, 57.805, 72.352, 6.746]
Example Output:
104.509