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.

Example Input: [3.556, 65.177]
Example Output: 34.366

Example Input: [206.606, -76.103, -16.863, 44.126, 4.019, 15.088]
Example Output: 29.479

Example Input: [97.555, 155.313, 12.48]
Example Output:
88.449

