You are given an integer n. On each step, you may subtract from it any one-digit number that appears in it.

How many steps are required to make the number equal to 0?

Input

One integer n (1 ≤ n ≤ 106).

Output

Print one integer: the minimum number of steps.

Explanation

An optimal solution is 27 → 20 → 18 → 10 → 9 → 0.