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: [202.409, 102.881, 14.035, -72.959, -17.121, 206.426, -57.984, 245.299, -86.478]

59.612