class Solution(object):
    def peakIndexInMountainArray(self, A):
        """
        :type A: List[int]
        :rtype: int
        """

        start = 1
        end = len(A) - 2



        while(start + 1 < end):
            mid = start + (end - start) // 2
            if A[mid-1] <= A[mid] <= A[mid+1]:
                start = mid
            elif A[mid+1] <= A[mid] <= A[mid-1]:
                end = mid
            else:
                return mid

        if A[start] < A[end]:
            return end
        else:
            return start