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: [-17.141, 203.132, -6.872, 155.222, -99.642]
Example Output: 46.94

Example Input: [1.435, 246.462, 5.433, -3.093, 31.948, 113.344, 41.816, 43.437, -93.129, 116.292]
Example Output: 50.395

Example Input: [171.844, 14.203, 177.919, 222.065, 116.848, 232.681]
Example Output:
155.927