1 #include <stdio.h>
2 #include <ctype.h>
3
4 int main() {
5 while(1) {
6 int sum = 0;
7 char c;
8 while(!isdigit(c=getchar()));
9 if(c=='0') break;
10 while(isdigit(c)) {
11 sum+= (c-'0');
12 c = getchar();
13 }
14 while(sum >= 10) {
15 int temp = sum;
16 sum = 0;
17 while(temp>0) {
18 sum += temp %10;
19 temp /= 10;
20 }
21 }
22 printf("%d\n", sum);
23 }
24 }