#include <bits/stdc++.h>
using namespace std;
using Int = long long;
const int mod = 1e9 + 7;
#define fast() cin.tie(0), ios::sync_with_stdio(false)

const Int MOD = 1e9 + 7; //<- alert!!!
typedef vector<Int> arr;
typedef vector<arr> mat;
inline arr mul(const mat &a, arr &b, Int mod)
{
    arr res(b.size(), 0);
    for (Int i = 0; i < (Int)b.size(); i++)
        for (Int j = 0; j < (Int)a[i].size(); j++)
            (res[i] += a[i][j] * b[j]) %= mod;
    return res;
}
inline mat mul(const mat &a, const mat &b, Int mod)
{
    mat res(a.size(), arr(b[0].size(), 0));
    for (Int i = 0; i < (Int)a.size(); i++)
        for (Int j = 0; j < (Int)b[0].size(); j++)
            for (Int k = 0; k < (Int)b.size(); k++)
                (res[i][j] += a[i][k] * b[k][j]) %= mod;
    return res;
}
inline mat mat_pow(mat a, Int n, Int mod)
{
    mat res(a);
    for (Int i = 0; i < (Int)a.size(); i++)
        for (Int j = 0; j < (Int)a[i].size(); j++)
            res[i][j] = (i == j);
    while (n)
    {
        if (n & 1)
            res = mul(a, res, mod);
        a = mul(a, a, mod);
        n >>= 1;
    }
    return res;
}

Int fib(Int a, Int b, Int n)
{
    mat A(2, arr(2));
    A[0][0] = a, A[0][1] = b, A[1][0] = 1, A[1][1] = 0;
    A = mat_pow(A, n, MOD);
    return A[1][0];
}

Int a, b, N;
int main()
{
    cin >> a >> b >> N;
    if (N == 0)
    {
        cout << 0 << endl;
        return 0;
    }
    else if (N == 1)
    {
        cout << 1 << endl;
        return 0;
    }
    Int ans = fib(a, b, N);
    cout << ans << endl;
}