> #include<stdio.h>
> int n;
> void find_digitalroot()
> {	
> 	int sum=100,count=0;
> 	while(sum>=10)
> 	{
> 		
> 		if(count>=1)
> 			n=sum;	
> 		sum=0;
> 		while(n>0)
> 		{
> 			sum+=n%10;
> 			n/=10;
> 		}
> 		count++;
>          }
> 	printf("%d\n",sum);
> }
> int main()
> {
> 	scanf("%d",&n);
> 	while(n!=0)
> 	{
> 		find_digitalroot();
> 		scanf("%d",&n);
> 	}
> 	return 0;
> }