#include "bits/stdc++.h"
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vl = vector<ll>;
using vvi = vector<vi>;
using vvl = vector<vl>;
const ll INF = 1LL << 60;
const ll MOD = 1000000007;
template <class T>
bool chmax(T &a, const T &b) {
    return (a < b) ? (a = b, 1) : 0;
}
template <class T>
bool chmin(T &a, const T &b) {
    return (b < a) ? (a = b, 1) : 0;
}
template <class C>
void print(const C &c, std::ostream &os = std::cout) {
    std::copy(std::begin(c), std::end(c), std::ostream_iterator<typename C::value_type>(os, " "));
    os << std::endl;
}

// mod int struct
// original : https://github.com/beet-aizu/library/blob/master/mod/mint.cpp

struct mint {
    ll v;
    ll mod;
    mint() : v(0) {}
    mint(signed v, ll mod = MOD) : v(v), mod(mod) {}
    mint(ll t, ll mod = MOD) : mod(mod) {
        v = t % mod;
        if (v < 0)
            v += mod;
    }

    mint pow(ll k) {
        mint res(1), tmp(v);
        while (k) {
            if (k & 1)
                res *= tmp;
            tmp *= tmp;
            k >>= 1;
        }
        return res;
    }

    static mint add_identity() { return mint(0); }
    static mint mul_identity() { return mint(1); }

    mint inv() { return pow(mod - 2); }

    mint &operator+=(mint a) {
        v += a.v;
        if (v >= mod)
            v -= mod;
        return *this;
    }
    mint &operator-=(mint a) {
        v += mod - a.v;
        if (v >= mod)
            v -= mod;
        return *this;
    }
    mint &operator*=(mint a) {
        v = 1LL * v * a.v % mod;
        return *this;
    }
    mint &operator/=(mint a) { return (*this) *= a.inv(); }

    mint operator+(mint a) const { return mint(v) += a; };
    mint operator-(mint a) const { return mint(v) -= a; };
    mint operator*(mint a) const { return mint(v) *= a; };
    mint operator/(mint a) const { return mint(v) /= a; };

    mint operator-() const { return v ? mint(mod - v) : mint(v); }

    bool operator==(const mint a) const { return v == a.v; }
    bool operator!=(const mint a) const { return v != a.v; }
    bool operator<(const mint a) const { return v < a.v; }

    // find x s.t. a^x = b
    static ll log(ll a, ll b) {
        const ll sq = 40000;
        unordered_map<ll, ll> dp;
        dp.reserve(sq);
        mint res(1);
        for (int r = 0; r < sq; r++) {
            if (!dp.count(res.v))
                dp[res.v] = r;
            res *= a;
        }
        mint p = mint(a).inv().pow(sq);
        res = b;
        for (int q = 0; q <= MOD / sq + 1; q++) {
            if (dp.count(res.v)) {
                ll idx = q * sq + dp[res.v];
                if (idx > 0)
                    return idx;
            }
            res *= p;
        }
        assert(0);
        return ll(-1);
    }

    static mint comb(long long n, int k) {
        mint num(1), dom(1);
        for (int i = 0; i < k; i++) {
            num *= mint(n - i);
            dom *= mint(i + 1);
        }
        return num / dom;
    }
};
ostream &operator<<(ostream &os, mint m) {
    os << m.v;
    return os;
}

template <size_t N, typename R>
struct SquareMatrix {
    using arr = array<R, N>;
    using mat = array<arr, N>;
    mat dat;

    SquareMatrix() {
        for (size_t i = 0; i < N; i++)
            for (size_t j = 0; j < N; j++)
                dat[i][j] = R::add_identity();
    }
    SquareMatrix &operator=(const SquareMatrix &a) {
        dat = a.dat;
        return (*this);
    }
    bool operator==(const SquareMatrix &a) const { return dat == a.dat; }

    size_t size() const { return N; };
    arr &operator[](size_t k) { return dat[k]; };
    const arr &operator[](size_t k) const { return dat[k]; };

    static SquareMatrix add_identity() { return SquareMatrix(); }
    static SquareMatrix mul_identity() {
        SquareMatrix res;
        for (size_t i = 0; i < N; i++)
            res[i][i] = R::mul_identity();
        return res;
    }

    SquareMatrix operator*(const SquareMatrix &B) const {
        SquareMatrix res;
        for (size_t i = 0; i < N; i++)
            for (size_t j = 0; j < N; j++)
                for (size_t k = 0; k < N; k++)
                    res[i][j] = res[i][j] + (dat[i][k] * B[k][j]);
        return res;
    }

    SquareMatrix operator+(const SquareMatrix &B) const {
        SquareMatrix res;
        for (size_t i = 0; i < N; i++)
            for (size_t j = 0; j < N; j++)
                res[i][j] = dat[i][j] + B[i][j];
        return res;
    }

    SquareMatrix pow(long long n) const {
        SquareMatrix a = *this, res = mul_identity();
        while (n) {
            if (n & 1)
                res = res * a;
            a = a * a;
            n >>= 1;
        }
        return res;
    }
};


int main() {
    ll a, b, n;
    cin >> a >> b >> n;
    if (n == 0) {
        cout << 0 << "\n";
        return 0;
    } else if (n == 1) {
        cout << 1 << "\n";
        return 0;
    }
    SquareMatrix<3, mint> arr;
    arr[0][1] = 1;
    arr[1][2] = 1;
    arr[2][1] = a;
    arr[2][2] = b;
    auto arrpow = arr.pow(n-2);
    mint ret = arrpow[2][0] * 0 + arrpow[2][1] * 1 + arrpow[2][2] * mint(a);
    cout << ret << "\n";
    return 0;
}