Digital Root Calculation

The digital root of a non-negative integer \(n\) is the single digit obtained by iteratively summing the digits of \(n\) until only one digit remains.

For example, the digital root \(f(n)\) is defined as follows:

\( f(n) = \begin{cases} n, & \text{if } n < 10 \\ f\Big(\sum_{\text{digits}} n\Big), & \text{if } n \ge 10 \end{cases} \)

Your task is to write a program that takes an integer as input and outputs its digital root.

inputFormat

The input consists of a single line containing one non-negative integer \(n\) (\(0 \leq n \leq 2^{31}-1\)).

outputFormat

Output a single line containing the digital root of \(n\).

## sample

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