def bbbsearch(A):
  start = 0
  end = len(A) - 1

  while (start <= end):
    mid = (start + end)/2

    if (A[mid] == mid):                      # i == A[i]
      if (mid == 0 or A[mid-1] != mid-1):
        return mid
      else:
        end = mid - 1
    elif (A[mid] < mid):
      start = mid + 1
    else:
      end = mid - 1

  # Fall-through: no match found
  return -1