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: [-18.341, 65.508, 39.034, 14.177, 215.222, 121.43, 0.83, 175.684, 1.246]

68.31