> #include "cstdio"
> 
> int main()
> {
> 	char buff[1000];
> 	int sum;
> 	while(scanf("%s",buff),buff[0]!='0')
> 	{
> 		sum=0;
> 		for(int i=0;buff[i];i++) sum+=buff[i]-'0';
> 		while(sum>9) sum=sum/10+sum%10;
> 		printf("%d\n",sum);
> 	}
> 	return 0;
> }