#include<bits/stdc++.h>
using namespace std;
int dp[20004];
int main(){
	int n,s,k;
	cin>>n>>s>>k;
	long long mod=1000000007;
	s=s-k*n*(n-1)/2;
	if(s<=0){
		cout<<0<<endl;
	}
	dp[0]=1;
	for(int i=n;i>=1;i--){
		for(int j=i;j<=s;j++){
			dp[j]=(dp[j-i]+dp[j])%mod;
		}
	}
	cout<<dp[s]<<endl;
}