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: [142.225, 243.809, -41.935, 96.795, -99.067, 222.292, 113.486, 143.726]
Example Output: 102.666

Example Input: [-19.64, 5.69, 102.211, 159.062, 7.744, 242.03, 141.431, 105.364, 40.338]
Example Output: 87.137

Example Input: [-83.979, -47.738, 246.23, 247.948, 110.267, -29.899, -93.927, -95.769]
Example Output:
31.642