#include <bits/stdc++.h>
#define rep(i, p, n) for (ll i = p; i < (ll)(n); i++)
#define rep2(i, p, n) for(ll i = p; i >= (ll)(n); i-- )
using namespace std;
using ll = long long;
double pi=3.141592653589793;
const long long inf=2*1e9;
const long long linf=8*1e18;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
//atcoder
#include <atcoder/modint>
#include <atcoder/dsu>
using namespace atcoder;
using mint1 = modint1000000007;
using mint2 = modint998244353;

int main() {
    ll N, S, K;
    cin >> N >> S >> K;
    S-=((N-1)*N/2)*K;
    if (S<0) {
    	cout << 0 << endl;
    	return 0;
    }
    vector<vector<mint1>> dp(S+1, vector<mint1>(N+1));
    rep(i, 0, N+1) {
        dp.at(0).at(i)=1;
    }
    rep(i, 0, S) {
        rep(j, 0, N+1) {
            mint1 A=0;
            if (j>0) {
                A=dp.at(i+1).at(j-1);
            }
            mint1 B=0;
            if ((i+1)>=j) {
                B=dp.at(i+1-j).at(j);
            }
            dp.at(i+1).at(j)=A+B;
        }
    }
    cout << dp.at(S).at(N).val();
}