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: [236.959, 159.123, 17.257, 241.561, 119.782, -3.56, -30.957]
Example Output: 105.738

Example Input: [57.506, 172.357, 191.473, 131.849]
Example Output: 138.296

Example Input: [134.479, 106.642, 94.798, 145.971, -88.732, 185.359, 49.87]
Example Output:
89.77