hdu 1013 Digital Roots

#include <cstdio>
#include <cstring>
#include <iostream>

using namespace std;

int main()
{
char s[10000];
while (scanf("%s",s)!=EOF)
{
int l=strlen(s);
if ((l==1)&&(s[0]='0')) break;
int sum=s[0]-48;
for (int i=1;i<l;i++) sum+=s[i]-48;
while (sum>9) sum=sum%10+sum/10;
printf("%d\n",sum);
}
return 0;
}