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: [67.255, -86.742, 213.212, 166.01, 63.505, 56.78, -11.841]

66.883