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

int main() {
	int n, s, k;
    cin >> n >> s >> k;
	for (int i = 0; i < n; i++) {
		s -= i * k;
	}
	int ans;
	if (s <= 0) {
		ans = 0;
	}
	else {
		long long dp[110][20010] = { 0 };
		dp[0][0] = 1;
		for (int i = 1; i <= n; i++) {
			for (int j = 0; j <= s; j++) {
				if (j >= i) {
					dp[i][j] = (dp[i - 1][j] + dp[i][j - i]) % 1000000007;
				}
				else {
					dp[i][j] = dp[i - 1][j];
				}
			}
		}
		ans = dp[n][s];
	}
	cout << ans << endl;
}