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: [57.506, 172.357, 191.473, 131.849]
Example Output: 138.296

Example Input: [187.54, -56.697, 55.301, 235.071, 176.682, 103.554, -35.29, 84.215]
Example Output: 93.797

Example Input: [102.961, 60.615, 165.588, 95.833, 129.047, -50.044, -45.609]
Example Output:
65.484