#include <bits/stdc++.h>
#define show(x) cerr << #x << " = " << x << endl
using namespace std;
using ll = long long;
using ld = long double;
constexpr ll MOD = 1000000007LL;
template <typename T>
constexpr T INF = numeric_limits<T>::max() / 10;
template <typename Functor>
struct fix_type
{
    Functor functor;
    template <typename... Args>
    decltype(auto) operator()(Args&&... args) const& { return functor(functor, std::forward<Args>(args)...); }
};
template <typename Functor>
fix_type<typename std::decay<Functor>::type> fix(Functor&& functor) { return {std::forward<Functor>(functor)}; }

ll N, B, D;
ll DINV;
ll power(const ll p, const ll n)
{
    if (n == 0) { return 1; }
    if (n % 2 == 1) {
        return power(p, n - 1) * p % MOD;
    } else {
        const ll pp = power(p, n / 2);
        return pp * pp % MOD;
    }
}
ll stone(ll i)
{
    return (((power(D + 1, i + 2) + MOD - 1) * DINV % MOD) + MOD - (i + 2)) % MOD;
}

int main()
{
    cin >> N >> B >> D;
    DINV = power(D, MOD - 2);
    ll ans = 0;
    ll rest = N;
    while (rest > 0) {
        int ind = 0;
        ll H = D + 1;
        for (; H - 1 <= rest; ind++, H *= (D + 1)) {
        }
        if (ind == 0) {
            ans += rest;
            rest = 0;
            continue;
        }
        const ll h = H / (D + 1);
        const ll sub = (stone(ind - 1) + (ind + 1)) % MOD;
        const ll rep = rest / h;
        rest = rest % h;
        (ans += rep * sub % MOD) %= MOD;
        if (rest == h - 1) {
            (ans += stone(ind - 1)) %= MOD;
            rest = 0;
        }
    }
    cout << (stone(B - 1) + MOD - ans) % MOD << endl;

    return 0;
}