Write a function that takes a list of integers and returns the number of peaks in the list. A peak is an element that is greater than both its immediate neighbours. The first and last elements of the list cannot be peaks because they only have one neighbour each. The list will contain at least three integers.
For example:
count_peaks([1, 3, 2, 4, 1]) → 2 (peaks at 3 and 4)count_peaks([1, 2, 3, 4, 5]) → 0count_peaks([5, 1, 5, 1, 5]) → 1