#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <iomanip>
#include <queue>
#include <algorithm>
#include <numeric>
#include <deque>
#include <sstream>

using namespace std;

#define debug(arg) print(#arg, arg)

// std::cerr << arg が元々使えるやつはそれを使う
template <class Tp> void out(Tp arg) {
  std::cerr << arg;
}
// std::pair の出力
template <class Tp1, class Tp2> void out(std::pair<Tp1, Tp2> arg) {
  std::cerr << '(';
  out(arg.first);
  std::cerr << ", ";
  out(arg.second);
  std::cerr << ')';
}
// std::tuple の出力
template <class T, std::size_t... Is> void print_tuple(T arg, std::index_sequence<Is...>) {
  static_cast<void>(((std::cerr << (Is == 0 ? "" : ", "), out(std::get<Is>(arg))), ...));
}
template <class... Ts> void out(std::tuple<Ts...> arg) {
  std::cerr << '(';
  print_tuple(arg, std::make_index_sequence<sizeof...(Ts)>());
  std::cerr << ')';
}
// std::{vector, deque, forward_list, list, initializer_list, set, multiset, unordered_set, unordered_multiset, map, multimap, unordered_map, unordered_multimap, valarray} の出力
template <template <class...> class Container, class... Ts>
void out(Container<Ts...> arg) {
  std::cerr << "[ ";
  std::for_each(std::cbegin(arg), std::cend(arg), [](typename Container<Ts...>::value_type elem) {
    out(elem);
    std::cerr << ' ';
  });
  std::cerr << ']';
}
// std::array の出力
template <class Tp, std::size_t N> void out(std::array<Tp, N> arg) {
  std::cerr << "[ ";
  std::for_each(std::cbegin(arg), std::cend(arg), [](Tp elem) {
    out(elem);
    std::cerr << ' ';
  });
  std::cerr << ']';
}

template <class Tp> void print(std::string_view name, Tp arg) {
  std::cerr << name << ": ";
  out(arg);  // out 関数を使うように変更
  std::cerr << '\n';
}

long long modc=1e9+7;

int main(){

    long long N, S, K;
    cin >> N >> S >> K;
    S -= (N*(N-1)/2)*K;
    if (S < 0){
        cout << 0 << endl;
        return 0;
    }

    vector<vector<long long>> dp(S+1, vector<long long>(N+1));
    dp[0][0] = 1;

    for (int n=0; n<=S; n++){
        for (int k=1; k<=N; k++){
            dp[n][k] = dp[n][k-1];
            if (n >= k){
                dp[n][k] += dp[n-k][k];
                dp[n][k] %= modc;
            }
        }
    }

    cout << dp[S][N] << endl;

    return 0;
}