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: [22.306, 72.768, 218.947, 52.973, 100.121, 157.59, -92.109]
Example Output: 76.085

Example Input: [198.958, 97.355]
Example Output: 148.156

Example Input: [141.148, 94.221, 81.692, 245.566]
Example Output:
140.657