#include <bits/stdc++.h>
using namespace std;
#define repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define rep(i,n) repl(i,0,n)
#define mp(a,b) make_pair((a),(b))
#define pb(a) push_back((a))
#define all(x) (x).begin(),(x).end()
#define uniq(x) sort(all(x)),(x).erase(unique(all(x)),end(x))
#define fi first
#define se second
#define dbg(x) cout<<#x" = "<<((x))<<endl
template<class T,class U> ostream& operator<<(ostream& o, const pair<T,U> &p){o<<"("<<p.fi<<","<<p.se<<")";return o;}
template<class T> ostream& operator<<(ostream& o, const vector<T> &v){o<<"[";for(T t:v){o<<t<<",";}o<<"]";return o;}

#define INF 2147483600
#define MOD 1000000007

long solve(){
  long n,s,k;
  cin>>n>>s>>k;

  s -= n*(n-1)/2*k;
  if(s<0) return 0;
  if(s==0) return 1;

  vector<long> dp(s+1, 0);
  dp[0]=1;
  rep(i,n){
    int x = n-i;
    vector<long> nxt(dp);
    repl(j,x, s+1) (nxt[j] += nxt[j-x])%=MOD;
    swap(dp,nxt);
  }
  return dp[s];
}

int main(){
  cout << solve() << endl;

  return 0;
}