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: [202.724, 129.438, -75.21, 114.102, 151.266]
Example Output: 104.464

Example Input: [135.575, 134.352, 209.54, 199.614, 87.027, 215.933, 49.266, 167.288, 164.589]
Example Output: 151.465

Example Input: [221.528, -3.778]
Example Output:
108.875