# ifndef ONLINE_JUDGE
# define _GLIBCXX_DEBUG
# endif
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using pii = pair<int, int>;
# define rep(i, n) for(int i = 0; i < (int)(n); ++i)
# define all(v) v.begin(), v.end()

int main(){
  constexpr char endl = '\n';
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout << fixed << setprecision(10);
  //input();
  int N, S, K;cin >> N >> S >> K;
  //solve();
  S -= (N-1)*N/2*K;
  if(S < 0){
    cout << 0 << endl;
    return 0;
  }
  int mod = 1e9+7;
  //dp[i][j]:=iのj分割の総和
  vvi dp(S+1, vi(N+1));
  dp[0][0] = 1;
  for(int i = 0; i <= S; ++i){
    for(int j = 1; j <= N; ++j){
      if(0 <= i-j)  dp[i][j] = dp[i-j][j]+dp[i][j-1];
      else  dp[i][j] = dp[i][j-1];
      dp[i][j] %= mod;
    }
  }
  //output();
  cout << dp[S][N] << endl;
}