#include<bits/stdc++.h>
using namespace std;
#include<atcoder/all>
using namespace atcoder;
#define rep(i,n) for(int i=0;i<(int)n;i++)
#define rep1(i,n) for(int i=1;i<=(int)n;i++)
using ll = long long;
using ull = unsigned long long;
using P = pair<int, int>;
using Pl = pair<ll, ll>;
using vi = vector<int>;
using vvi = vector<vi>;
using vd = vector<double>;
using vs = vector<string>;
using vb = vector<bool>;
using vvb = vector<vb>;
using vl = vector<long long>;
using vvl = vector<vl>;
#define inf 2147483642//int max
#define linf 900000000000000000
const double PI = 3.1415926535897932384626433832795028841971;
template<typename T>inline bool chmax(T& a, T b) { return ((a < b) ? (a = b, true) : (false)); }
template<typename T>inline bool chmin(T& a, T b) { return ((a > b) ? (a = b, true) : (false)); }
long long llceil(long long a, long long b) { if (a % b == 0) { return a / b; }return (a / b) + 1; }
#define yes cout<<"Yes"<<endl;
#define no cout<<"No"<<endl;
#define yesno(ans) cout<<(ans?"Yes":"No")<<endl;
#define sortu(a) sort(a.begin(),a.end());



int main() {
	//分割DP

	ll n, s, k; cin >> n >> s >> k;

	ll zub = s - n*(n - 1)/2 * k;//最低何円

	//これをn分割
	ll M = 1e9 + 7;
	if (zub <0) {
		cout << 0 << endl;
		return 0;
	}


	vvi dp(n+1, vi(zub+1));
	dp[0][0] = 1;
	for (int i = 1; i <= n; i++) {
		for (int j = 0; j <= zub; j++) {
			if (j - i >= 0) {
				dp[i][j] = (dp[i - 1][j] + dp[i][j - i]) % M;
			}
			else {
				dp[i][j] = dp[i - 1][j];
			}
		}
	}

	cout << dp[n][zub] << endl;

	



	return 0;
}