> #include<iostream.h>
> #include<string.h>
> 
> void main()
> {
> 	char num[100];
> 	int i,sum,a;
> 
> 	while(strcmp(num,"0")!=0){
> 		cin>>num;
> 		if (strcmp(num,"0")==0)
> 			break;
> 		if (strlen(num)==1){
> 			cout<<num<<endl;
> 			continue;
> 		}
> 		sum=0;
> 		for (i=0;i<int(strlen(num));i++)
> 			sum+=num[i]-'0';
> 		a=100;
> 		while(a>=10){
> 			a=0;
> 			while(sum!=0){
> 				a+=sum%10;
> 				sum=sum/10;
> 			}
> 			sum=a;
> 		}
> 		cout<<a<<endl;
> 	}
> }