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: [131.164, 99.999, 138.488, 57.264, -40.069, -82.402, -42.836]
Example Output: 37.373

Example Input: [-2.772, 225.483, 211.749, 45.779, -82.623, 229.799, 107.783, 64.653]
Example Output: 99.981

Example Input: [162.188, 184.691, -69.948, 122.5, 1.153, -21.48, -82.005, 210.977, -85.877, -62.758]
Example Output:
35.944