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: [219.769, -36.26, 3.121, -22.5, 124.372]
Example Output: 57.7

Example Input: [70.496, 183.122, 75.017, -19.287, 53.364, -12.389, 249.47, -88.484, 249.98, 35.226]
Example Output: 79.652

Example Input: [31.132, 184.696, 139.797, -24.276, 59.448, 55.704, -20.415, 230.881]
Example Output:
82.121