#include <bits/stdc++.h>
using namespace std;
//#include <atcoder/all>
//using namespace atcoder;
using ll=long long;
using Graph=vector<vector<int>>;
#define MAX 1000000
#define MOD 1000000007
//#define INF 1000000000
#define INF 1000000000000000000

int main(){
  int N,S,K;
  cin>>N>>S>>K;
  if(S<N*(N-1)/2*K){
    cout<<0<<endl;
    return 0;
  }
  S-=N*(N-1)/2*K;
  //cout<<S<<endl;
  vector<ll> dp(S+1,0);
  dp[S]=1;
  for(int cnt=1;cnt<=N;cnt++){
    for(int i=S-cnt;i>=0;i--){
      dp[i]+=dp[i+cnt];
      dp[i]%=MOD;
    }
  }
  cout<<dp[0]<<endl;
}