#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <map>
#include <unordered_map>
#include <set>
#include <bitset>
#include <iomanip>
#include <math.h>
#include <queue>
#include <numeric>
#include <cassert>
using namespace std;

const int mod = 1000000007;
struct mint {
  typedef long long ll;
  ll x;
  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 { return mint(*this) += a;}
  mint operator-(const mint a) const { return mint(*this) -= a;}
  mint operator*(const mint a) const { return mint(*this) *= 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 { return mint(*this) /= a;}
};
istream& operator>>(istream& is, mint& a) { return is >> a.x;}
ostream& operator<<(ostream& os, const mint& a) { return os << a.x;}

int main() {
  int N, S, K;
  cin >> N >> S >> K;
  S -= K*N*(N-1)/2;
  if (S < 0) {
    printf("0\n");
    return 0;
  }

  vector<vector<mint>> dp(N+1, vector<mint>(S+1, 0));
  dp[0][0] = 1;
  for (int i = 1; i <= N; i++)
    for (int j = 0; j <= S; j++) {
      if (j-i >= 0) dp[i][j] = dp[i-1][j] + dp[i][j-i];
      else dp[i][j] = dp[i-1][j];
    }

  printf("%lld\n", dp[N][S].x);

  return 0;
}