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: [186.566, -69.519, 103.877, 84.507, 217.205, 81.764, 10.501, 105.596, 208.834, -99.939]

82.939