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: [237.501, 67.08, 13.857]
Example Output: 106.146

Example Input: [70.282, -54.718, 95.793, 94.043, 183.314]
Example Output: 77.743

Example Input: [188.835, 4.769, 77.899, 173.178, -98.747]
Example Output:
69.187