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: [138.63, 106.759, 86.625]
Example Output: 110.671

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

Example Input: [-75.075, 22.238, -90.64, 238.928]
Example Output:
23.863

