1 #include <stdio.h>
 2 #include <math.h>
 3 #include <algorithm>
 4 #define max(a,b) a>b?a:b 
 5 using namespace std;
 6 int main()
 7 {
 8 
 9     int a, b, c;
10     int i, total;
11     
12     while(~scanf("%d %d %d", &a, &b, &c))
13     {
14         total = 0;
15         int num[3] = {0, 0, 0};
16         if(abs(a-b)%3==0)
17             num[total] += max(a,b);
18         total++;
19         if(abs(b-c)%3==0)
20             num[total] += max(b,c);
21         total++;
22         if(abs(a-c)%3==0)
23             num[total] += max(a,c);
24         total++;
25         if(num[0]==0 && num[1]==0 && num[2]==0)
26         printf("):\n");
27         else
28         {
29             sort(num, num+3);
30             for(i=0; i<3; i++)
31             {
32                 if(num[i] != 0)
33                 {
34                     printf("%d\n",num[i]);
35                     break; 
36                 }
37             }
38         }
39     }
40     return 0;
41 }