#include <bits/stdc++.h>

using namespace std;

const long long MOD = 1e9 + 7;

long long solve(int n, int s, int k) {
  int r = s;
  for (int i = 0; i < n; i++)
    r -= i * k;

  if (r == 0) return 1;
  if (r < 0) return 0;

  vector<vector<long long> > dp(n + 1, vector<long long>(r + 1));
  dp[0][0] = 1;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j <= r; j++) {
      if (j-n+i >= 0) {
        dp[i+1][j] += (dp[i][j-n+i] + dp[i+1][j-n+i]) % MOD;
        dp[i+1][j] %= MOD;
      }
    }
    for (int j = 0; j <= r; j++) {
      dp[i+1][j] += dp[i][j];
      dp[i+1][j] %= MOD;
    }
  }

  return dp[n][r];
}


int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  
  int n, s, k;
  cin >> n >> s >> k;
  cout << solve(n, s, k) << endl;
  
  return 0;
}