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: [138.526, 60.81, 233.845, -33.602, 189.784, 13.888, 184.543, 53.635, 18.299, -87.132]
Example Output: 77.26

Example Input: [-58.447, 213.433, 187.859, 103.704]
Example Output: 111.637

Example Input: [50.509, -86.99, 195.287, -94.237, -88.852, 159.071, 62.31, 236.829, 166.143]
Example Output:
66.674