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: [57.506, 172.357, 191.473, 131.849]
Example Output: 138.296

Example Input: [161.683, 162.041, 187.429, -79.681, 60.809, 225.806]
Example Output: 119.681

Example Input: [125.987, 140.164, 103.07, -78.923, -92.734, -96.888]
Example Output:
16.779