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: [21.723, 130.05, 75.095]
Example Output: 75.623

Example Input: [21.007, 48.739, -49.831, -22.699]
Example Output: -0.696

Example Input: [192.74, 78.623, -5.937, 144.535]
Example Output:
102.49