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: [-45.826, -27.376, 126.782, -28.164, 213.819, 186.676]
Example Output: 70.985

Example Input: [85.354, -22.629, 51.171, 238.376, 177.126, -90.135, -84.086, 175.426, -80.74]
Example Output: 49.985

Example Input: [217.868, 100.747, 186.392, -90.949, 234.492, 121.106]
Example Output:
128.276