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: [-25.508, 206.576, 233.062, 12.247, 129.526, 108.984, 200.861]

123.678