 The "external path length" is the sum of the lengths of all unique external paths.If there are formula_2 elements, which is a positive integer, and the external path length is formula_135, then the average number of iterations for an unsuccessful search formula_136, with the one iteration added to count the initial iteration.The external path length is divided by formula_137 instead of formula_2 because there are formula_137 external paths, representing the intervals between and outside the elements of the array.