#include <iostream>
#include <cstdio>
#include <string>
#include <algorithm>
#include <utility>
#include <cmath>
#include <vector>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <tuple>
#include <numeric>
#include <functional>
using namespace std;
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vector<ll>> vvl;
typedef pair<ll, ll> P;
#define rep(i, n) for(ll i = 0; i < n; i++)
#define exrep(i, a, b) for(ll i = a; i <= b; i++)
#define out(x) cout << x << endl
#define exout(x) printf("%.10f\n", x)
#define chmax(x, y) x = max(x, y)
#define chmin(x, y) x = min(x, y)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define pb push_back
#define re0 return 0
const ll mod = 1000000007;
const ll INF = 1e16;

int main() {
    ll n, s, k;
    cin >> n >> s >> k;

    ll x = s - k * (n - 1) * n / 2;
    
    if(x < 0) {
        out(0);
        re0;
    }

    vvl dp(x+1, vl(n+1));  // dp[i][j] : iをj個以下に分割する方法の数
    dp[0][1] = 1;
    exrep(i, 0, x) {
        exrep(j, 1, n) {
            dp[i][j] += dp[i][j-1];
            if(i - j >= 0) {
                dp[i][j] += dp[i - j][j];
            }
            dp[i][j] %= mod;
        }
    }

    out(dp[x][n]);
    re0;
}