using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        var n = NN;
        var c = NList;
        var (b, d) = (c[0], c[1]);
        var ans = V(b, d);
        var len = new long[31];
        len[1] = d;
        var size = new long[31];
        size[1] = d;
        for (var i = 2; i < 31; ++i)
        {
            len[i] = len[i - 1] * (d + 1) + d;
            size[i] = (size[i - 1] * (d + 1) + (long)d * i) % mod;
            if (n <= len[i])
            {
                var rest = (long)n;
                for (var j = i; j > 0; --j)
                {
                    if (rest == 0) break;
                    if (len[j] == n)
                    {
                        rest = 0;
                        ans = (ans - size[j] + mod) % mod;
                    }
                    else
                    {
                        var ok = 0;
                        var ng = d + 1;
                        while (ng - ok > 1)
                        {
                            var mid = (ok + ng) / 2;
                            if ((len[j - 1] + 1) * mid <= rest) ok = mid;
                            else ng = mid;
                        }
                        rest -= (len[j - 1] + 1) * ok;
                        ans = (ans - (size[j - 1] + j) * ok % mod + mod) % mod;
                    }
                }
                WriteLine(ans);
                return;
            }
        }
    }
    static int mod = 1_000_000_007;
    static long V(int b, int d)
    {
        return (Exp(d + 1, 2) * (Exp(d + 1, b - 1) - 1 + mod) % mod * Exp(d, mod - 2) % mod + d - b + 1 + mod) % mod;
    }
    static long Exp(long n, long p)
    {
        long _n = n % mod;
        var _p = p;
        var result = 1L;
        if ((_p & 1) == 1) result *= _n;
        while (_p > 0)
        {
            _n = _n * _n % mod;
            _p >>= 1;
            if ((_p & 1) == 1) result = result * _n % mod;
        }
        return result;
    }
}