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

signed main()
{
	const int MOD = 1000000007;
	int N, S, K;
	cin >> N >> S >> K;

	S -= N * (N - 1) * K / 2;
	if (S < 0) {
		cout << 0 << endl;
		return 0;
	}

	vector<vector<int>> dp(N + 1, vector<int>(S + 1, 0));
	dp[0][0] = 1;

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

	cout << dp[N][S] << endl;
	return 0;
}