#include <iostream>#include <string>using namespace std;int main(){   string n; while(cin>>n,n!="0"){    int s=0,l=n.length();      for(int i=0;i<l;i++)    s+=n[i]-‘0‘;  while(s>9)   s=s/10+s%10;  cout<<s<<endl;}return 0;}

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#include <iostream>
#include <string>
using namespace std;
int main()
{
   string n;
 while(cin>>n,n!="0")
{
    int s=0,l=n.length();
   
  for(int i=0;i<l;i++)    s+=n[i]-‘0‘;
 
while(s>9)   s=s/10+s%10;
  cout<<s<<endl;
}
return 0;
}