#include <iostream>
#include <vector>
#define repeat(i,n) for (int i = 0; (i) < (n); ++(i))
#define repeat_reverse(i,n) for (int i = (n)-1; (i) >= 0; --(i))
using namespace std;
const int mod = 1e9 + 7;
int main() {
    int n, s, k; cin >> n >> s >> k;
    s -= k * (n - 1) * n / 2;
    if (s < 0) {
        cout << 0 << endl;
    }
    else {
        vector<int> dp(s + 1);
        dp[0] = 1;
        repeat(i, n) {
            repeat_reverse(j, s + 1) {
                for (int a = 1; j + a * (n - i) < s + 1; ++a) {
                    dp[j + a * (n - i)] += dp[j];
                    dp[j + a * (n - i)] %= mod;
                }
            }
        }
        cout << dp[s] << endl;
    }
    return 0;
}