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: [245.2, 202.565]
Example Output: 223.882

Example Input: [73.603, -84.154, 222.739, 205.594, 215.842]
Example Output: 126.725

Example Input: [5.688, 217.21]
Example Output:
111.449

