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: [99.278, 72.353, -21.292]
Example Output: 50.113

Example Input: [236.753, 184.794, -45.415, 20.278, -41.34, 109.146, 176.83]
Example Output: 91.578

Example Input: [215.934, -33.238, 32.705]
Example Output:
71.8