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: [-89.59, -15.783, 35.306, 46.851, 97.275, 19.027, 200.372, 62.551]
Example Output: 44.501

Example Input: [201.917, 240.159, 36.615]
Example Output: 159.564

Example Input: [17.937, 84.657, 31.917, -38.543, -13.699, 203.232, 92.297, -51.317]
Example Output:
40.81