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: [-55.82, -68.866, 159.882, 227.351, 224.405, 170.123, -26.867]

90.03