#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int N, S, K;
  cin >> N >> S >> K;

  ll dp[S+1][N+1];
  memset(dp, 0, sizeof(dp));
  dp[0][0] = 1;
  ll mod = 1e9+7;

  for(int i=0;i<=S;i++) {
    for(int j=1;j<=N;j++) {
      dp[i][j] = dp[i][j-1];
      if(i-j >= 0)
        dp[i][j] += dp[i-j][j];
      dp[i][j] %= mod;
    }
  }

  ll x = S;
  for(int i=0;i<N;i++)
    x -= i*K;
  if(x < 0)
    cout << 0 << endl;
  else
    cout << dp[x][N] << endl;
}