Definition: 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.
Input: [34.772, 69.758, 51.194, 75.304, -97.212, 214.056, 122.222, 134.099, 102.886]

78.564