#include <bits/stdc++.h>
using namespace std;
#define rep(i, m, n) for (int i = m; i < n; ++i)
const long long MOD = 1000000007;

using vec = vector<long long>;
using Mat = vector<vec>;

Mat Mul(Mat A, Mat B) {
    Mat C(A.size(), vec(B[0].size()));
    rep(i, 0, A.size()) rep(k, 0, B.size()) rep(j, 0, B[0].size()) {
        C[i][j] = (C[i][j] + A[i][k] * B[k][j]) % MOD;
    }
    return C;
}

Mat Pow(Mat A, long long n) {
    int SZ = A.size();
    Mat B(SZ, vec(SZ));
    rep(i, 0, SZ) B[i][i] = 1;
    while(n > 0) {
        if(n & 1) B = Mul(B, A);
        A = Mul(A, A);
        n >>= 1;
    }
    return B;
}

int main() {
    long long a, b, n;
    cin >> a >> b >> n;
    Mat A(2, vec(2));
    A[0][0] = a; A[0][1] = b;
    A[1][0] = 1LL; A[1][1] = 0LL;
    A = Pow(A, n);
    cout << A[1][0] << endl;
    return 0;
}