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: [139.6, 119.652, 135.338, 171.029, 247.554, 222.19, -61.931, 120.928, 235.688]
Example Output: 147.783

Example Input: [57.205, -33.98, 111.608, -83.731, 107.658]
Example Output:
31.752