You are given an integer $n$ . On each step, you may subtract one of the digits from the number.
How many steps are required to make the number equal to $0$ ?
The only input line has an integer $n$ .
Print one integer: the minimum number of steps.
27\n
5\n
An optimal solution is $27 \rightarrow 20 \rightarrow 18 \rightarrow 10 \rightarrow 9 \rightarrow 0$ .