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: [75.879, 43.123]
Example Output: 59.501

Example Input: [125.67, 5.514, 161.93, 107.05, 118.949, 233.815, 230.211]
Example Output: 140.448

Example Input: [193.404, 201.757, 196.22, 170.051, -15.837]
Example Output:
149.119