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: [53.126, 235.803, 214.379, -13.572, 204.492, 157.953, -86.192, 62.323, 100.931]

103.249