#include <bits/stdc++.h>
using namespace std;
#define all(v) (v).begin(), (v).end()
using ll = long long;
using ld = long double;
using pint = pair<int, int>;
using pll = pair<ll, ll>;

ll MOD = 1e9 + 7;
ll dp[20202];

int main() {
    int N, S, K; cin >> N >> S >> K;
    S -= N*(N-1)/2*K;
    dp[0] = 1;
    for (int i = 1; i <= N; i++) {
        for (int j = 0; j <= S; j++) {
            dp[i+j] += dp[j];
            dp[i+j] %= MOD;
        }
    }
    cout << (S >= 0 ? dp[S] : 0) << endl;
    return 0;
}