#include using namespace std; using ll = long long; using ld = long double; using VI = vector; using VL = vector; template using PQ = priority_queue, greater>; #define FOR(i,a,n) for(int (i)=(a);(i)<(n);++(i)) #define eFOR(i,a,n) for(int (i)=(a);(i)<=(n);++(i)) #define rFOR(i,a,n) for(int (i)=(n)-1;(i)>=(a);--(i)) #define erFOR(i,a,n) for(int (i)=(n);(i)>=(a);--(i)) #define each(i, a) for(auto &i : a) #define SORT(i) sort((i).begin(),(i).end()) #define rSORT(i,a) sort((i).begin(),(i).end(),(a)) #define all(i) (i).begin(),(i).end() #define out(y,x) ((y) < 0 || h <= (y) || (x) < 0 || w <= (x)) #define line cout << "------------------------\n" #define ENDL(i,n) ((i) == (n) - 1 ? "\n" : " ") #define stop system("pause") //comment out this on AOJ. constexpr ll INF = 1000000000; constexpr ll LLINF = 1LL << 60; constexpr ll mod = 1000000007; constexpr ll MOD = 998244353; constexpr ld eps = 1e-10; //1e-9? constexpr ld pi = 3.1415926535897932; templateinline bool chmax(T& a, T b) { if (a < b) { a = b; return true; }return false; } templateinline bool chmin(T& a, T b) { if (a > b) { a = b; return true; }return false; } inline void init() { cin.tie(nullptr); cout.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); } templateinline istream& operator>>(istream& is, vector& v) { for (auto& elemnt : v)is >> elemnt; return is; } templateinline istream& operator>>(istream& is, pair& p) { is >> p.first >> p.second; return is; } templateinline vector vec(size_t a) { return vector(a); } templateinline vector defvec(T def, size_t a) { return vector(a, def); } templateinline auto vec(size_t a, Ts... ts) { return vector(ts...))>(a, vec(ts...)); } templateinline auto defvec(T def, size_t a, Ts... ts) { return vector(def, ts...))>(a, defvec(def, ts...)); } int main() { init(); int n, s, k; cin >> n >> s >> k; s -= n * (n - 1) / 2 * k; if (s < 0) { cout << "0\n"; return 0; } auto dp = vec(n + 1, s + 1); dp[0][0] = 1; eFOR(i, 1, n)eFOR(j, 0, s) { dp[i][j] = dp[i - 1][j]; if (i <= j)(dp[i][j] += dp[i][j - i]) %= mod; } cout << dp[n][s] << "\n"; }