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: [85.354, -22.629, 51.171, 238.376, 177.126, -90.135, -84.086, 175.426, -80.74]
Example Output: 49.985

Example Input: [70.485, 231.704, -98.046, -30.011, 80.665, 168.282, 224.41]
Example Output: 92.498

Example Input: [213.397, 128.836, 91.588, 84.087]
Example Output:
129.477