POJ 1519

#include <iostream>
#include <string>
using namespace std;
int itsucks(string const& digit){
   unsigned int x=0,y;
   for(int i=0;i<digit.length();x%=9,++i)x+=digit[i]-'0';
   return x==0?9:x;
}
int main(){
   for(string str;cin>>str&&str!="0";cout<<itsucks(str)<<endl);
   return 0;
}