#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>
#include <stack>
#include <algorithm>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#include <cstdlib>
#include <bitset>
#include <tuple>
#include <assert.h>
#include <fstream>
#include <bitset>
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

const long long INF = 1LL << 60;
const long long MOD = 1000000007LL;
const long long MAX = 500000LL;
using namespace std;
typedef unsigned long long ull;
typedef  long long ll;

ll N, S, K;
vector<vector<ll>> dp;
ll dfs(ll n, ll k) {
	if (k == 1) return 1;
	if (dp[n][k] != -1) return dp[n][k];
	ll res = 0;
	res += dfs(n, k - 1);
	res %= MOD;
	if (n - k >= 0)
		res += dfs(n - k, k);
	res %= MOD;
	return dp[n][k] = res;
}
int main()
{
	cin >> N >> S >> K;
	dp = vector<vector<ll>>(S + 1, vector<ll>(N + 1, -1));
	ll sum = 0;
	for (ll i = 0; i < N; i++) {
		S -= i * K;
	}
	if (S < 0) {
		cout << "0" << endl;
		return 0;
	}
	cout << dfs(S, N) << endl;
	return 0;
}