#include<iostream>
#include<string>
#include<vector>
#include<utility>
#include<algorithm>
#include<map>
#include<cstdlib>
#include<cmath>
#include<numeric>
#include<iomanip>
#include<functional>
#include<cstdlib>
#include<queue>
#include<deque>
#include <iterator>     // std::back_inserter
const double PI = acos(-1);
using namespace std;
using ll =long long;
#define rep(i,n)for(ll i=0;i<(n);i++)
const int mod = 1000000007;
const ll inf = 1e18+1;
int ctoi(char c) {
	if (c >= '0' && c <= '9') {
		return c - '0';
	}
	return 0;
}

ll gcd(ll a, ll b) {
	if (a % b == 0) {
		return b;
	}
	else {
		return gcd(b, a % b);
	}
}
ll lcm(ll a, ll b) {
	return a * b / gcd(a, b);
};
//fixed << setprecision(2)
template<class T> inline bool chmin(T& a, T b) {
	if (a > b) {
		a = b;
		return true;
	}
	return false;
}
template<class T> inline bool chmax(T& a, T b) {
	if (a < b) {
		a = b;
		return true;
	}
	return false;
}
//小文字=大文字+32
int main() {
	ll N,S,K;
	cin >> N>>S>>K;
	S -= K*(N - 1) * N / 2;
	if (S < 0) {
		cout << 0;
		return 0;
	}
	vector<vector<ll>>dp(N+1,vector<ll>(S+1,0));
	dp[0][0] = 1;
	for(ll i=1;i<N+1;i++){
		for (ll j = 0; j < S+1; j++) {
			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];
}