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: [-12.713, 52.148, 221.074, 194.73, -19.277, -13.807, 114.31, 181.762, 247.685]

107.324