Problems

# How many times to repeat?

# How many times to repeat?

The positive integer $n$ is given. We subtract from this number the sum of its digits. From the received number we soon subtract the sum of its digits and so on. This operation continues until the number is positive. How many times this operation will be repeated?

#### Input

One number $n$$(0 < n < 2 \cdot 10^9)$.

#### Output

The amount of performed operations.

Input example #1

21

Output example #1

3