#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define defprint(i) cout << i << endl
using namespace std;
using ll = long long;
using P = pair<int,int>;

const int mod = 1000000007;
struct mint {
  ll x; // typedef long long ll;
  mint(ll x=0):x((x%mod+mod)%mod){}
  mint operator-() const { return mint(-x);}
  mint& operator+=(const mint a) {
    if ((x += a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator-=(const mint a) {
    if ((x += mod-a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator*=(const mint a) {
    (x *= a.x) %= mod;
    return *this;
  }
  mint operator+(const mint a) const {
    mint res(*this);
    return res+=a;
  }
  mint operator-(const mint a) const {
    mint res(*this);
    return res-=a;
  }
  mint operator*(const mint a) const {
    mint res(*this);
    return res*=a;
  }
  mint pow(ll t) const {
    if (!t) return 1;
    mint a = pow(t>>1);
    a *= a;
    if (t&1) a *= *this;
    return a;
  }

  // for prime mod
  mint inv() const {
    return pow(mod-2);
  }
  mint& operator/=(const mint a) {
    return (*this) *= a.inv();
  }
  mint operator/(const mint a) const {
    mint res(*this);
    return res/=a;
  }
};


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