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: [-6.992, -36.177, -95.203, 87.142]
Example Output: -12.808

Example Input: [-17.106, 23.8, -54.195, 233.82, -99.732, -68.488, 215.616]
Example Output: 33.388

Example Input: [-75.699, -32.585]
Example Output:
-54.142