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: [135.807, 205.755, 191.805]
Example Output: 177.789

Example Input: [166.542, 216.326, 98.969, -96.779, 33.532]
Example Output: 83.718

Example Input: [134.362, 95.641, 171.541, 167.562, 6.713, -22.782]
Example Output:
92.173

