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: [218.807, 72.849, 7.838, 124.81, 45.929, 239.888]
Example Output: 118.354

Example Input: [234.272, 196.413, -92.425]
Example Output: 112.753

Example Input: [-84.257, 150.346, 115.489, 233.173, -21.974, -78.979, 60.098, 122.944, 41.603]
Example Output:
59.827