#include <bits/stdc++.h>
using namespace std;
using ll=int64_t;
#define rep(i,n) for(int i=0;i<(n);++i)
const ll MOD =1e9+7;
int main(){
	int N,S,K;
	cin>>N>>S>>K;
	vector<vector<ll>> dp(N,vector<ll>(S+1));
	dp[0][0] = 1;
	for(int i=0;i<N;i++){
		for(int j=1;j<=S;j++){
			if(j-(N-i)>=0) dp[i][j] += dp[i][j-(N-i)];
			if(i>0&&j-K*(N-i)>=0) dp[i][j] = (dp[i][j]+dp[i-1][j-K*(N-i)])%MOD;
		}
	}
	cout<<dp[N-1][S]<<"\n";
}