#include <iostream>
#define int long long
using namespace std;

int mod = 1000000007;

int power(int a, int n) {
	if (n == 0) return 1;
	if (n & 1) return (a * power(a, n - 1));
	return power(a * a, n / 2);
}

int powmod(int a, int n, int mod) {
	if (n == 0) return 1;
	if (n & 1) return (a * powmod(a, n - 1, mod)) % mod;
	return powmod((a * a) % mod, n / 2, mod);
}

int fs(int b, int d) {
	int res = (d + 1) * (powmod(d + 1, b, mod) + mod - 1) % mod * powmod(d, mod - 2, mod) % mod;
	return (res + mod - b) % mod;
}

int fn(int b, int d) {
	return power(d + 1, b) - 1;
}

int n, b, d;

signed main() {
	int i;
	
	cin >> n >> b >> d;
	
	int ans = fs(b, d);
	for (i = 0; fn(i, d) <= n; i++); i--;
	
	for (; i >= 0; i--) {
		int res = power(d + 1, i);
		int syo = n / res;
		int hiku = syo * (fs(i, d) + i + 1) % mod;
		ans = (ans + mod - hiku) % mod;
		n %= res;
	}
	cout << ans << endl;
	return 0;
}