#include<sstream>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<string>
#include<vector>
#include<set>
#include<map>
#include<queue>
#include<numeric>
#include<functional>
#include<algorithm>
#include<bitset>
using namespace std;
#define INF (1<<29)
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define all(v) v.begin(),v.end()
#define uniq(v) v.erase(unique(all(v)),v.end())
#define indexOf(v,x) (find(all(v),x)-v.begin())

#define MOD 1000000007


int main(){
	int n,s,k;
	cin>>n>>s>>k;
	s-=(n-1)*k*n/2;
	if(s<0){
		cout<<0<<endl;
		return 0;
	}
	vector<int> dp(s+1,0);
	dp[0]=1;
	for(int i=1;i<=n;i++){
		rep(j,s-i+1){
			dp[j+i]+=dp[j];
			dp[j+i]%=MOD;
		}
	}
	cout<<dp[s]<<endl;

	return 0;
}