1 #include <algorithm>
 2 #include <iostream>
 3 #include <iomanip>
 4 #include <cstring>
 5 #include <climits>
 6 #include <complex>
 7 #include <fstream>
 8 #include <cassert>
 9 #include <cstdio>
10 #include <bitset>
11 #include <vector>
12 #include <deque>
13 #include <queue>
14 #include <stack>
15 #include <ctime>
16 #include <set>
17 #include <map>
18 #include <cmath>
19
20 using namespace std;
21
22 const int maxn = 10;
23 typedef struct Matrix {
24     int m[maxn][maxn];
25     int r;
26     int c;
27     Matrix(){
28         r = c = 0;
29         memset(m, 0, sizeof(m));
30     }
31 } Matrix;
32
33 Matrix mul(Matrix m1, Matrix m2, int mod) {
34     Matrix ans = Matrix();
35     ans.r = m1.r;
36     ans.c = m2.c;
37     for(int i = 1; i <= m1.r; i++) {
38         for(int j = 1; j <= m2.r; j++) {
39                for(int k = 1; k <= m2.c; k++) {
40                 if(m2.m[j][k] == 0) continue;
41                 ans.m[i][k] = ((ans.m[i][k] + m1.m[i][j] * m2.m[j][k] % mod) % mod) % mod;
42             }
43         }
44     }
45     return ans;
46 }
47
48 Matrix quickmul(Matrix m, int n, int mod) {
49     Matrix ans = Matrix();
50     for(int i = 1; i <= m.r; i++) {
51         ans.m[i][i]  = 1;
52     }
53     ans.r = m.r;
54     ans.c = m.c;
55     while(n) {
56         if(n & 1) {
57             ans = mul(m, ans, mod);
58         }
59         m = mul(m, m, mod);
60         n >>= 1;
61     }
62     return ans;
63 }
64
65 int a, b, n, m;
66
67 int main() {
68     // freopen("in", "r", stdin);
69        m = 7;
70     while(~scanf("%d %d %d", &a, &b, &n)) {
71         Matrix p;
72         while(a < 0) a += m;
73         while(b < 0) b += m;
74         p.r = 2, p.c = 1;
75         p.m[1][1] = 1;
76         p.m[2][1] = 1;
77         if(n <= 4) {
78             printf("%d\n", p.m[4-n+1][1] % m);
79             continue;
80         }
81         Matrix s;
82         s.r = s.c = 2;
83         s.m[1][1] = a, s.m[1][2] = b;
84         s.m[2][1] = 1, s.m[2][2] = 0;
85         s = quickmul(s, n-2, m);
86         int ans = 0;
87         for(int i = 1; i <= p.r; i++) {
88             ans = (ans + (p.m[i][1] * s.m[1][i]) % m) % m;
89         }
90         printf("%d\n", ans % m);
91     }
92     return 0;
93 }