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: [38.343, 177.478, 120.174, -74.923, 98.159]
Example Output: 71.846

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

Example Input: [236.267, 92.062, -95.005, -85.155, 120.483]
Example Output:
53.73