#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define rep(i, n) for (ll i = 0; i < n; i++)
#define FOR(i, a, b) for (ll i = a; i < b; i++)
#define len(v) ll(v.size())
#define fi first
#define se second

template <class T>
void cout_vec(const vector<T> &vec){
  for(auto itr:vec) cout<<itr<<' ';
  cout<<endl;
}

typedef pair<ll,ll> P;
const ll mod=1e9+7;
const ll inf=1e15;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n,s,k;
    cin>>n>>s>>k;
    if(s-k*n*(n-1)/2<0){
      cout<<0<<endl;
      return 0;
    }
    vector<vector<ll>> dp(s+10,vector<ll>(n+10,0));
    dp[0][0]=1;
    rep(i,s+1)FOR(j,1,n+1){
      if(i>=j) dp[i][j]=(dp[i-j][j]+dp[i][j-1])%mod;
      else dp[i][j]=dp[i][j-1];
    }
    cout<<dp[s-k*n*(n-1)/2][n]<<endl;
}