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: [215.561, -18.128]
Example Output: 98.716

Example Input: [169.737, 56.872, 102.557, -9.77]
Example Output: 79.849

Example Input: [146.01, 72.871, 207.695, -63.833, 13.201, 231.713, 173.995]
Example Output:
111.665