#include <bits/stdc++.h>
using namespace std;
using T = long long;
using vvt = vector<vector<T>>;
constexpr long long MOD = 1e9+7;


vvt identity_mat(int n){
    vvt I(n, vector<T>(n, 0));
    for (int i = 0; i != n; ++i) I[i][i] = 1;
    return I;
}

vvt matmul(const vvt & a, const vvt & b, const long long mod = MOD){
    int n_row = a.size();
    int n_col = b[0].size();
    assert(a[0].size() == b.size());
    vvt c(n_row, vector<T>(n_col, 0));
    for (int i = 0; i != n_row; ++i){
        for (int j = 0; j != n_col; ++j){
            for (int k = 0; k != b.size(); ++k){
                c[i][j] = (c[i][j] + a[i][k] * b[k][j]) % mod;
            }
        }
    }
    return c;
}

vvt matpow(vvt mat, long long n, const long long mod = MOD){
    // a^n を求める。
    assert(mat.size() == mat[0].size());
    vvt ans = identity_mat(mat.size());
    while (n){
        if (n & 1) ans = matmul(ans, mat, mod);
        mat = matmul(mat, mat, mod);
        n >>= 1;
    }
    return ans;
}

int main(){
    long long a, b, n;
    cin >> a >> b >> n;
    vvt mat = {{a, b}, {1LL, 0LL}};
    auto p = matpow(mat, n);
    cout << p[1][0] << endl;
    return 0;
}