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: [-1.31, 169.522, -26.172, 111.289]
Example Output: 63.332

Example Input: [218.46, 7.937, 155.624, 82.813, 93.516]
Example Output: 111.67

Example Input: [233.719, 11.512, 159.737, -55.121, 2.157]
Example Output:
70.401