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: [102.553, 221.594, -69.406, 192.534, 139.703, -38.208, 228.963, 32.921]
Example Output: 101.332

Example Input: [70.568, -80.778]
Example Output: -5.105

Example Input: [51.455, 84.02, 192.884, 197.216, 4.149, -1.558, 97.546, 75.979, -81.102]
Example Output:
68.954