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: [243.395, -41.82, -93.746, -1.05, 185.63, 107.755, 141.745, 237.202, -42.654]

81.829