/* #region Head */ #include using namespace std; using ll = long long; using ull = unsigned long long; using ld = long double; using pll = pair; template using vc = vector; template using vvc = vc>; using vll = vc; using vvll = vvc; using vld = vc; using vvld = vvc; using vs = vc; using vvs = vvc; template using um = unordered_map; template using pq = priority_queue; template using pqa = priority_queue, greater>; #define REP(i, m, n) for (ll i = (m), i##_len = (ll)(n); i < i##_len; ++(i)) #define REPM(i, m, n) for (ll i = (m), i##_max = (ll)(n); i <= i##_max; ++(i)) #define REPR(i, m, n) for (ll i = (m), i##_min = (ll)(n); i >= i##_min; --(i)) #define REPD(i, m, n, d) for (ll i = (m), i##_len = (ll)(n); i < i##_len; i += (d)) #define REPMD(i, m, n, d) for (ll i = (m), i##_max = (ll)(n); i <= i##_max; i += (d)) #define REPI(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++) #define ALL(x) begin(x), end(x) #define SIZE(x) ((ll)(x).size()) #define PERM(c) \ sort(ALL(c)); \ for (bool c##p = 1; c##p; c##p = next_permutation(ALL(c))) #define UNIQ(v) v.erase(unique(ALL(v)), v.end()); #define endl '\n' #define sqrt sqrtl constexpr ll INF = 1'010'000'000'000'000'017LL; constexpr ll MOD = 1'000'000'007LL; // 1e9 + 7 constexpr ld EPS = 1e-12; constexpr ld PI = 3.14159265358979323846; // vector 入力 template istream &operator>>(istream &is, vc &vec) { for (T &x : vec) is >> x; return is; } // vector 出力 (for dump) template ostream &operator<<(ostream &os, vc &vec) { ll len = SIZE(vec); os << "{"; for (int i = 0; i < len; i++) os << vec[i] << (i == len - 1 ? "" : ", "); os << "}"; return os; } // vector 出力 (inline) template ostream &operator>>(ostream &os, vc &vec) { ll len = SIZE(vec); for (int i = 0; i < len; i++) os << vec[i] << (i == len - 1 ? "\n" : " "); return os; } // pair 入力 template istream &operator>>(istream &is, pair &pair_var) { is >> pair_var.first >> pair_var.second; return is; } // pair 出力 template ostream &operator<<(ostream &os, pair &pair_var) { os << "(" << pair_var.first << ", " << pair_var.second << ")"; return os; } // map 出力 template ostream &operator<<(ostream &os, map &map_var) { os << "{"; REPI(itr, map_var) { os << *itr; itr++; if (itr != map_var.end()) os << ", "; itr--; } os << "}"; return os; } // um 出力 template ostream &operator<<(ostream &os, um &map_var) { os << "{"; REPI(itr, map_var) { os << *itr; auto itrcp = itr; itrcp++; if (itrcp != map_var.end()) os << ", "; } os << "}"; return os; } // set 出力 template ostream &operator<<(ostream &os, set &set_var) { os << "{"; REPI(itr, set_var) { os << *itr; itr++; if (itr != set_var.end()) os << ", "; itr--; } os << "}"; return os; } // dump #define DUMPOUT cerr void dump_func() { DUMPOUT << endl; } template void dump_func(Head &&head, Tail &&... tail) { DUMPOUT << head; if (sizeof...(Tail) > 0) { DUMPOUT << ", "; } dump_func(move(tail)...); } // chmax (更新「される」かもしれない値が前) template > bool chmax(T &xmax, const U &x, Comp comp = {}) { if (comp(xmax, x)) { xmax = x; return true; } return false; } // chmin (更新「される」かもしれない値が前) template > bool chmin(T &xmin, const U &x, Comp comp = {}) { if (comp(x, xmin)) { xmin = x; return true; } return false; } // ローカル用 #define DEBUG_ #ifdef DEBUG_ #define DEB #define dump(...) \ DUMPOUT << " " << string(#__VA_ARGS__) << ": " \ << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]" \ << endl \ << " ", \ dump_func(__VA_ARGS__) #else #define DEB if (false) #define dump(...) #endif struct AtCoderInitialize { static constexpr int IOS_PREC = 15; static constexpr bool AUTOFLUSH = false; AtCoderInitialize() { ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); cout << fixed << setprecision(IOS_PREC); if (AUTOFLUSH) cout << unitbuf; } } ATCODER_INITIALIZE; string yes = "Yes", no = "No"; // string yes = "YES", no = "NO"; /* #endregion */ struct mint { ll x; mint(ll x = 0) : x((x % MOD + MOD) % MOD) {} 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) 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; } // O(log(t)) mint pow(ll t) const { if (!t) return 1; mint a = pow(t >> 1); // ⌊t/2⌋ 乗 a *= a; // ⌊t/2⌋*2 乗 if (t & 1) // ⌊t/2⌋*2 == t-1 のとき a *= *this; // ⌊t/2⌋*2+1 乗 => t 乗 return a; } // for prime mod mint inv() const { return pow(MOD - 2); // オイラーの定理から, x^(-1) ≡ x^(p-2) } mint &operator/=(const mint a) { return (*this) *= a.inv(); } mint operator/(const mint a) const { mint res(*this); return res /= a; } bool operator==(const mint a) const { return this->x == a.x; } bool operator==(const ll a) const { return this->x == a; } // mint 入力 friend istream &operator>>(istream &is, mint &x) { is >> x.x; return is; } // mint 出力 friend ostream &operator<<(ostream &os, mint x) { os << x.x; return os; } }; /** Problem */ void solve() { ll n, d, k; cin >> n >> d >> k; vc> dp(2, vc(k + 1, 0)); dp[0][0] = 1; // REP(j, max(0LL, (i - 1) / 2), max(1LL, min(i, n))) REPM(j, 1, n) { fill(ALL(dp[j % 2]), 0LL); REPM(i, j, min(k, j * d)) { // dump(j, i); dp[j % 2][i] = dp[j % 2][i - 1]; dp[j % 2][i] += dp[(j - 1) % 2][i - 1]; if (i - 1 - d >= 0) dp[j % 2][i] -= dp[(j - 1) % 2][i - 1 - d]; } } // dump(dp); cout << dp[n % 2][k] << endl; } /** * エントリポイント. * @return 0. */ int main() { solve(); return 0; }