1 #include <iostream>
2 #include <algorithm>
3 #include <cmath>
4 #define MOD 7
5 #define N 2
6 using namespace std;
7
8 struct Matrix
9 {
10 long long v[N][N];
11 };
12
13 //矩阵间的乘法%m
14 Matrix matrix_mul(Matrix A, Matrix B, long long m)
15 {
16 Matrix ans;
17
18 for (int i = 0; i < N; i++)
19 {
20 for (int j = 0; j < N; j++)
21 {
22 ans.v[i][j] = 0;
23 for (int k = 0; k < N; k++)
24 {
25 ans.v[i][j] += (A.v[i][k] * B.v[k][j]) % m;
26 }
27 ans.v[i][j] %= m;
28 }
29 }
30 return ans;
31 }
32
33 //矩阵快速幂c^n%m
34 Matrix matrix_pow(Matrix C, long long n, long long m)
35 {
36 Matrix ans = { 1, 0, 0, 1 };//e
37 while (n)
38 {
39 if (n & 1)
40 ans = matrix_mul(ans, C, m);
41 C = matrix_mul(C, C, m);
42 n >>= 1;
43 }
44 return ans;
45 }
46
47 int main()
48 {
49 long long n;
50 int a, b;
51 cin >> a >> b >> n;
52 Matrix temp1 = { (a%MOD + MOD) % MOD, (b%MOD + MOD) % MOD, 1, 0 };
53 Matrix temp2 = { 1, 0, 1, 0 }; // temp2{f[2],0,f[1],0}!!!!!
54
55 if (n < 2)
56 {
57 cout << 1 << endl;
58 return 0;
59 }
60 Matrix res = matrix_pow(temp1, n - 2, MOD);
61 res = matrix_mul(res, temp2, MOD);
62 cout << res.v[0][0] << endl;
63 return 0;
64 }
