// No.269 見栄っ張りの募金活動
#include <iostream>
#include <vector>
using namespace std;
typedef long long ll;
const ll mod = 1'000'000'007;

int main() {
    int N, S, K;
    cin >> N >> S >> K;

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

    vector<vector<ll>> dp(N + 1, vector<ll>(S - N * (N - 1) / 2 * K + 1, 0));
    dp[0][0] = 1;
    for (int i = 1; i <= N; ++i) {
        for (int j = 0; j <= S - N * (N - 1) / 2 * K; ++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[N][S - N * (N - 1) / 2 * K] << endl;
}