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: [-32.31, 239.275, 136.79, 31.099, -54.56, -33.907, 19.999]

43.769