Problem Description

A function f(n) recursively calls itself until the sum of digits of n becomes a single digit. Count the total number of function calls made.

Input Format

A single positive integer n.

Output Format

Total number of function calls made until single digit is reached.

Constraints

• 1 ≤ n ≤ 10^9

• Count includes the initial call

• Single digit means 0-9

• Sum digits repeatedly until single digit

• Example: 999 → 27 → 9 (3 calls total)

Sample Input/Output

Explanation

f(999): sum=27, call f(27). f(27): sum=9, call f(9). f(9): single digit, stop. Total calls: 3.