hdu 1013 Digital Roots

//求数根

#include<stdio.h>
int fun(int a);
int main()
{
    int a;
    char c;
    while(1)
    {
            scanf("%c",&c);
            if(c=='0')
            break;
            a=c-'0';
            while(scanf("%c",&c)!=EOF)
            {
                                      if(c=='\n')
                                      break;
                                      a=fun(a+c-'0');
            }
            printf("%d\n",a);
            }
            return 0;
    }
    int fun(int a)
    {
        int s=0;
        while(a>0)
        {
                  s+=a%10;
                  a/=10;
        }
        return s;
    }