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: [248.385, -40.468, -97.132]
Example Output: 36.928

Example Input: [157.423, -98.775, -67.748, 25.759, 24.697, 150.289, -68.457, 212.57, -9.355]
Example Output: 36.267

Example Input: [98.666, -84.275, 14.739]
Example Output:
9.71