1 #include<cstdio>
 2 #include<iostream>
 3 #include<cstring>
 4 #include<algorithm>
 5 #include<cmath>
 6 using namespace std;
 7 struct Mtr{
 8     int a , b , c , d ;
 9     Mtr operator * (const Mtr m) const
10     {
11         Mtr res ;
12         res.a = (a*m.a%7 + b*m.c%7)%7;
13         res.b = (a*m.b%7+b*m.d%7)%7;
14         res.c = (c*m.a%7+d*m.c%7)%7;
15         res.d = (c*m.b%7+d*m.d%7)%7;
16         return res;
17     }
18 };
19 int cal(Mtr a , int n)
20 {
21     Mtr c;
22     c.a = c.d = 1;
23     c.b = c.c = 0;
24     while(n>0)
25     {
26         if(n&1)
27             c = c*a;
28         a = (a*a);
29         n/=2;
30     }
31     return (c.a+c.b)%7;
32 }
33 int main()
34 {
35     int a , b , n;
36     while(~scanf("%d%d%d",&a,&b,&n)&&(a!=0||b!=0||n!=0))
37     {
38         Mtr tm;
39         tm.a = a;
40         tm.b = b;
41         tm.c = 1;
42         tm.d = 0;
43         int tt = cal(tm,n-2);
44         printf("%d\n",tt);
45     }
46     return 0;
47 }