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: [-60.041, -56.779, 6.2, 73.114, 137.319]
Example Output: 19.963

Example Input: [-61.563, 49.659, 125.562, 130.542, 75.232, 197.442, 175.182, 54.736, 210.833, 65.27]
Example Output: 102.289

Example Input: [-89.318, 247.959, 25.441, -92.763, 172.246, -57.286, 181.58]
Example Output:
55.408