#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;

const static int NIL = -1;
const long long INF = 1LL << 60;
typedef long long ll;
typedef unsigned long long ull;

bool is_debug = false;
int ini = 1000000001;
ll mod = 1000000007;

int main(){
	int n, s, k;
	cin >> n >> s >> k;
	for(int i = 0; i < n; i++){
		s -= i * k;
	}
	if(s < 0){
		cout << 0 << endl;
		return 0;
	}
	int m = n;
	n = s;
	vector<vector<int>> dp(m + 1, vector<int>(n + 1, 0));
	dp[0][0] = 1;
	for(int i = 1; i <= m; i++){
		for(int j = 0; j <= n; j++){
			if(j - i >= 0){
				dp[i][j] = (dp[i][j - i] + dp[i - 1][j]) % mod;
			}else{
				dp[i][j] = dp[i - 1][j];
			}
		}
	}

	cout << dp[m][n] << endl;
}