Digital Root
Repeatedly sum digits until a single digit remains.
Input format
One line with a single integer N.
Output format
Repeatedly add N's digits until one digit remains, and print that digit (ignore the sign).
Constraints
- Values fit in a 64-bit signed integer
- Trailing whitespace and a trailing newline are ignored by the judge
Read from stdin, write to stdout. Sample cases below show the exact format.
Sample cases
Example 1
Input
0Expected output
0Example 2
Input
9Expected output
9