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: [-98.361, -84.91]
Example Output: -91.636

Example Input: [216.087, 41.07, 213.683, 53.822, 31.214]
Example Output: 111.175

Example Input: [24.538, -63.143, -78.392, 195.006, 137.039, 107.973]
Example Output:
53.837