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: [-17.106, 23.8, -54.195, 233.82, -99.732, -68.488, 215.616]
Example Output: 33.388

Example Input: [242.148, 97.472, -15.031, 246.784, 54.233, -27.114]
Example Output: 99.749

Example Input: [13.21, 76.551, 51.016, 230.763, 149.792, 157.216, 117.414, 144.272, 5.805, 118.165]
Example Output:
106.42