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: [5.703, -17.365, 21.827, 38.836, 5.17, -15.533]
Example Output: 6.44

Example Input: [207.804, 175.122, 13.63, 217.625, -98.484]
Example Output: 103.139

Example Input: [240.244, 248.235, 65.086]
Example Output:
184.522