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: [26.595, 220.402, -36.236, -79.382, -17.51, -71.282]
Example Output: 7.098

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

Example Input: [122.376, -68.918, -0.307, 6.323, -52.407]
Example Output:
1.413