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: [171.439, 0.981, 42.253, 239.995, 129.938, -67.125, -69.565, -53.374, -51.357]
Example Output: 38.132

Example Input: [-32.03, 84.065, 91.512, 156.512, 78.808, 165.396, 176.764, 116.6]
Example Output: 104.703

Example Input: [204.241, -12.158, 204.326, 79.389, 76.223, 38.435, 219.868, 12.41, 181.717]
Example Output:
111.606