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: [231.057, 71.527, 201.799, -5.17, -14.963, -35.693]
Example Output: 74.76

Example Input: [231.159, 217.795, 230.676, -11.951, -82.697, 31.413]
Example Output: 102.732

Example Input: [169.344, 51.979, 150.113, 6.619, -60.536, 134.488, -90.731]
Example Output:
51.611