#include <iostream>
#include <string>
#include <vector>
#include <cstdlib>
#include <cstdio>
#include <cmath>
#include <algorithm>
#include <map>
#include <stack>
#include <queue>
#include <set>
#include <cstring>

using namespace std;
// ascending order
#define vsort(v) sort(v.begin(), v.end())
// descending order
#define vsort_r(v) sort(v.begin(), v.end(), greater<int>())
#define vunique(v) unique(v.begin(), v.end())
#define mp make_pair
#define ts(x) to_string(x)
#define rep(i, a, b) for(int i = (int)a; i < (int)b; i++)
#define repm(i, a, b) for(int i = (int)a; i > (int)b; i--)
#define bit(a) bitset<8>(a)
typedef long long ll;
typedef pair<int, int> P;
const ll INF = 1e18;

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);

	ll N, S, K;
	cin >> N >> S >> K;


	S = S - N * (N - 1) / 2 * K;
	ll dp[N + 1][S + 1];

	ll mod = 1e9 + 7;
	memset(dp, 0, sizeof(dp));
	dp[0][0] = 1;
	rep(i, 1, N + 1) rep(j, 0, S + 1) {
		if(j - i >= 0) dp[i][j] = (dp[i - 1][j] + dp[i][j - i]) % mod;
		else dp[i][j] = dp[i - 1][j];
	}
	cout << dp[N][S] << endl;
}