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: [126.177, 120.225, 231.498, 170.694, 34.361, 101.823, -21.468, 234.339]
Example Output: 124.706

Example Input: [-30.529, 129.329, 69.69]
Example Output:
56.163