Definition: 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.
Input: [138.598, 55.677, 18.483, 226.852, 75.885, -65.561, 8.468, 203.355]

82.72