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: [-1.817, 129.363, 197.437, 181.521, 249.901, 56.704, 130.786, -1.69, 21.456, 88.586]

105.225