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: [-33.711, -36.057, 246.847, 91.06, 151.965, 10.053, 20.21]

64.338