#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;
const int MOD = (int)1e9 + 7;

int main() {
    int n, s, k; cin >> n >> s >> k;
    s -= k * (n - 1) * n / 2;
    if (s < 0) {
        cout << 0 << endl;
        return 0;
    }
    vector<int> dp(s + 1);
    dp[0] = 1;
    for (int i = 1; i <= n; i++) {
        for (int j = 0; j + i <= s; j++) {
            (dp[j + i] += dp[j]) %= MOD;
        }
    }
    cout << dp[s] << endl;
    return 0;
}