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: [-77.355, -39.914, -58.481, 126.87, 215.247, 225.51, 194.059, 15.129, 196.666, 26.548]

82.428