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: [155.467, -40.717, -24.529, -22.608, 38.752]
Example Output: 21.273

Example Input: [-57.838, -63.616, 49.646, -45.262, 73.1, -82.399, 47.168]
Example Output: -11.314

Example Input: [94.577, -53.428, -32.952, -47.368, -62.93, 186.486, -67.365, -31.864, 33.448, 247.086]
Example Output:
26.569