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: [20.538, 100.835, -23.197, 207.707, -12.758, 152.97, 190.404]
Example Output: 90.928

Example Input: [202.724, 129.438, -75.21, 114.102, 151.266]
Example Output: 104.464

Example Input: [78.782, 45.834, 148.226, 183.431]
Example Output:
114.068