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: [-13.411, 77.937, 17.74, 206.933, -30.457, -61.065, -64.628, 111.316, 133.259]

41.958