1 #include<stdio.h>
2 #include<stdlib.h>
3 #include<string.h>
4
5 char s[1001];
6 int Roots(int x)
7 {
8 int num=0,i;
9 while( x )
10 {
11 num += x%10;
12 x /= 10;
13 }
14 if(num < 10)
15 return num;
16 else
17 return Roots(num);
18 }
19
20 int main()
21 {
22 int sum,i, ans;
23
24 while(scanf("%s",s) != EOF)
25 {
26 if(s[0] == '0') break;
27 sum = 0;
28 for(i=0; i<strlen(s); i++)
29 sum += (s[i]-'0');
30 if(sum < 10)
31 {
32 printf("%d\n",sum);
33 }
34 else
35 {
36 ans = Roots(sum);
37 printf("%d\n",ans);
38 }
39
40 }
41 return 0;
42 }
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