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: [-27.766, 75.259, 84.057, 203.297, 187.359, 115.348, 30.845, 102.126, -33.413]

81.901