/** * @FileName a.cpp * @Author kanpurin * @Created 2020.10.23 03:48:53 **/ #include "bits/stdc++.h" using namespace std; typedef long long ll; template< int MOD > struct mint { public: long long x; mint(long long x = 0) :x((x%MOD+MOD)%MOD) {} mint(std::string &s) { long long z = 0; for (int i = 0; i < s.size(); i++) { z *= 10; z += s[i] - '0'; z %= MOD; } this->x = z; } mint& operator+=(const mint &a) { if ((x += a.x) >= MOD) x -= MOD; return *this; } mint& operator-=(const mint &a) { if ((x += MOD - a.x) >= MOD) x -= MOD; return *this; } mint& operator*=(const mint &a) { (x *= a.x) %= MOD; return *this; } mint& operator/=(const mint &a) { long long n = MOD - 2; mint u = 1, b = a; while (n > 0) { if (n & 1) { u *= b; } b *= b; n >>= 1; } return *this *= u; } mint operator+(const mint &a) const { mint res(*this); return res += a; } mint operator-() const {return mint() -= *this; } mint operator-(const mint &a) const { mint res(*this); return res -= a; } mint operator*(const mint &a) const { mint res(*this); return res *= a; } mint operator/(const mint &a) const { mint res(*this); return res /= a; } friend std::ostream& operator<<(std::ostream &os, const mint &n) { return os << n.x; } friend std::istream &operator>>(std::istream &is, mint &n) { long long x; is >> x; n = mint(x); return is; } bool operator==(const mint &a) const { return this->x == a.x; } bool operator!=(const mint &a) const { return this->x != a.x; } mint pow(long long k) const { mint ret = 1; mint p = this->x; while (k > 0) { if (k & 1) { ret *= p; } p *= p; k >>= 1; } return ret; } }; constexpr int MOD = 1e9 + 7; template struct Combination { private: int N; public: vector< T > FACT, IFACT; Combination(int n) : N(n) { FACT.resize(n + 1); IFACT.resize(n + 1); FACT[0] = 1; IFACT[0] = 1; for (int i = 1; i <= n; i++) { FACT[i] = FACT[i - 1] * i; IFACT[i] = T(1) / FACT[i]; } } T comb(int n, int r) { if (n < 0 || r < 0 || r > n) return 0; if (r > n / 2) r = n - r; return FACT[n] * IFACT[n - r] * IFACT[r]; } }; int main() { int n,k,d;cin >> n >> k >> d; int m = n % (k-1); int t = n / (k-1); if (m == 0) { m = k-1; t--; } if (d == 1) { cout << m << endl; return 0; } Combination> cb(2000001); mint ans = 0; for (int i = 0; i <= t; i++) { ans += cb.comb(m-2+t-i,t-i) * mint(d).pow(i) * m; } cout << ans << endl; return 0; }