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: [29.292, 193.26, -48.646]
Example Output: 57.969

Example Input: [-58.447, 213.433, 187.859, 103.704]
Example Output: 111.637

Example Input: [204.618, 145.758, 163.317]
Example Output:
171.231