The easier problem Beat the previous asked you to greedily extract a strictly ascending sequence of integers from the given series of digits. For example, for digits equal to "31415926", the array of integers returned should be [3, 14, 15, 92], with the last original digit left unused.

Going somewhat against intuition, the ability to tactically skip some of the digits at will may allow the resulting array of integers to contain more elements than the list constructed in the previous greedy fashion. With this additional freedom, the example digit string "31415926" would allow the result [3, 4, 5, 9, 26] with one more element than the greedily constructed solution.

Your function should return the length of the longest array of ascending integers that can be extracted from digits. Note that you are allowed to skip one or more digits not just between two integers being extracted, but during the construction of each such integer.

Input: String (string).

Output: Integer (number).

Examples:

assert.strictEqual(staircase("100123"), 4);
assert.strictEqual(staircase("503715"), 4);
assert.strictEqual(staircase("0425494220946"), 6);
assert.strictEqual(staircase("04414952075836"), 7);

The mission was taken from Python CCPS 109. It is taught for Ryerson Chang School of Continuing Education by Ilkka Kokkarinen