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: [223.951, 2.518, 140.336, -38.799, 217.497, 212.153, 21.874]
Example Output: 111.361

Example Input: [150.294, -80.748, 28.474]
Example Output:
32.673