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: [93.405, -31.061]
Example Output: 31.172

Example Input: [109.74, 169.0, 195.864, -1.043, 51.968, -56.564, 214.711, -78.61, 212.459, 228.74]
Example Output: 104.626

Example Input: [53.064, -94.606]
Example Output:
-20.771