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: [-57.334, 24.995, 72.22, -78.376, 218.297, 203.999, 21.93, -20.246, 15.97]
Example Output: 44.606

Example Input: [164.048, 94.225, 164.003, -19.198, 47.156, 4.59, 170.668, 156.371, -13.172, -27.61]
Example Output: 74.108

Example Input: [-57.334, 24.995, 72.22, -78.376, 218.297, 203.999, 21.93, -20.246, 15.97]
Example Output:
44.606