#include <bits/stdc++.h>
using namespace std;
using ll=long long;
ll I=167167167167;
ll Q=1e9+7;

vector<vector<ll>> vec2(ll a,ll b,ll syoki){
  vector<vector<ll>> c(a,vector<ll>(b,syoki));
  return c;
}

int main() {
	ll N,S,K;
	cin>>N>>S>>K;
	S-=(K*N*(N-1))/2;
	if(S<0){
		cout<<"0"<<endl;
		return 0;
	}
	auto dp=vec2(S+2*N,N+2,0);
	dp[0][0]=1;
	for(int i=0;i<=S;i++){
		for(int j=0;j<=N;j++){
			dp[i][j]%=Q;
			if(j!=0) dp[i+j][j]+=dp[i][j];
			dp[i][j+1]+=dp[i][j];
		}
	}
	cout<<dp[S][N]<<endl;
}