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.

[21.531, 221.161, -31.194]
70.499

[-17.141, 203.132, -6.872, 155.222, -99.642]
46.94

[243.307, 121.756]

182.532