Digital Root of a Product

Given two non-negative integers x and y, compute the digital root of their product.

The digital root of a number \(n\) is given by:

$$ \text{dr}(n) = \begin{cases} 0, & \text{if } n = 0, \\ 1 + ((n - 1) \bmod 9), & \text{if } n > 0. \end{cases} $$

Your task is to read the two integers from stdin, compute \(x \times y\), then output its digital root to stdout.

inputFormat

The input consists of two non-negative integers x and y separated by space.

Example:

5 7

outputFormat

Output a single integer which is the digital root of the product of x and y.

Example:

8

## sample

5 7

8

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