#include #define rep(i,n) for (int i = 0; i < (n); i ++) using namespace std; using ll = long long; using PL = pair; using P = pair; constexpr int INF = 1000000000; constexpr long long HINF = 1000000000000000; constexpr long long MOD = 1000000007;// = 998244353; constexpr double EPS = 1e-4; constexpr double PI = 3.14159265358979; template struct ModInt { long long x; ModInt(long long x = 0) :x((x%Modulus + Modulus)%Modulus) {} constexpr ModInt &operator+=(const ModInt a) {if ((x += a.x) >= Modulus) x -= Modulus; return *this;} constexpr ModInt &operator-=(const ModInt a) {if ((x += Modulus - a.x) >= Modulus) x -= Modulus; return *this;} constexpr ModInt &operator*=(const ModInt a) {(x *= a.x) %= Modulus; return *this;} constexpr ModInt &operator/=(const ModInt a) {return *this *= a.inverse();} constexpr ModInt operator+(const ModInt a) const {return ModInt(*this) += a.x;} constexpr ModInt operator-(const ModInt a) const {return ModInt(*this) -= a.x;} constexpr ModInt operator*(const ModInt a) const {return ModInt(*this) *= a.x;} constexpr ModInt operator/(const ModInt a) const {return ModInt(*this) /= a.x;} friend constexpr ostream& operator<<(ostream& os,const ModInt& a) {return os << a.x;} friend constexpr istream& operator>>(istream& is,ModInt& a) {return is >> a.x;} ModInt inverse() const {// x ^ (-1) long long a = x,b = Modulus,p = 1,q = 0; while (b) {long long d = a/b; a -= d*b; swap(a,b); p -= d*q; swap(p,q);} return ModInt(p); } ModInt pow(long long N) {// x ^ N ModInt a = 1; while (N) { if (N&1) a *= *this; *this *= *this; N >>= 1; } return a; } }; using mint = ModInt<1000000007>; mint dp[105][2005]; int main() { int N,S,K; cin >> N >> S >> K; rep(i,N) S -= i*K; rep(i,N + 1) dp[i][0] = 1; rep(i,N)rep(j,S) { dp[i + 1][j + 1] = dp[i][j + 1]; if (j - i >= 0) dp[i + 1][j + 1] += dp[i + 1][j - i]; } cout << dp[N][S] << '\n'; return 0; }