Given the task definition and input, reply with output. In this task you are given a list of numbers and you need to find the average of each two consecutive values. The average of two numbers a and b is calculated as: (a + b) /2. The output should be a list of the averages of each two consecutive values. A list is presented with two brackets and comma-separated values, like: [1,2,3].

[33, 14, 59, -39, 70, 51, -86, 31, -15]

[23.5, 36.5, 10.0, 15.5, 60.5, -17.5, -27.5, 8.0]