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: [108.822, 139.139, 130.938, 100.996, 155.361, 8.752, 221.639, -12.877]
Example Output: 106.596

Example Input: [121.069, 12.661, 159.825, -39.645, 6.609, 156.735, 110.054, 112.875]
Example Output: 80.023

Example Input: [247.206, 219.694, -46.551, -8.901, 16.075, 247.831]
Example Output:
112.559