#include<cstdio>#include<string>#include<cstring>#include<iostream>usingnamespace std;
string n;intmain(){while(cin>>n,n!="0"){int len = n.size();int ans =0;for(int i =0;i < len;i++){
ans =(int)(((longlong)ans*10+n[i]-'0')%9);}if(ans==0) ans=9;printf("%d\n",ans);}return0;}