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.

Example Input: [-86.423, 157.154, 69.563, -67.516, 147.66, 216.018, 213.404]
Example Output: 92.837

Example Input: [217.523, 92.701, -55.65, -89.359, 55.742, 158.634, -31.883, 206.554]
Example Output: 69.283

Example Input: [243.048, -51.461, 74.679, 169.541, -41.639]
Example Output:
78.834