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: [53.417, 108.293, 81.325, 0.115, 69.127, 149.459, -4.859]

65.268