For a positive integer n, let f(n) denote the sum of the digits
of n when represented in base 10. It is easy to see that the sequence of
numbers n, f(n), f(f(n)), f(f(f(n))), ... eventually becomes a single digit
number that repeats forever. Let this single digit be denoted g(n).
For example, consider n = 1234567892. Then:
f(n) = 1+2+3+4+5+6+7+8+9+2 = 47 f(f(n)) = 4+7 = 11 f(f(f(n))) = 1+1 = 2
Therefore, g(1234567892) = 2.
Each line of input contains a single positive integer n at most 2,000,000,000.
For each such integer, you are to output a single line containing g(n).
Input is terminated by n = 0 which should not be processed.
2 11 47 1234567892 0
2 2 2 2