#include<iostream> #include<algorithm> #include<string> #include<vector> #include<cmath> #include<map> #include<random> #include<iomanip> #include<queue> #include<stack> #include<assert.h> #include<time.h> #define int long long #define double long double #define rep(i,n) for(int i=0;i<n;i++) #define REP(i,n) for(int i=1;i<=n;i++) #define ggr getchar();getchar();return 0; #define prique priority_queue constexpr auto mod = 998244353; #define inf 1e15 #define key 1e9 using namespace std; typedef pair<int, int>P; template<class T> inline void chmax(T& a, T b) { a = std::max(a, b); } template<class T> inline void chmin(T& a, T b) { a = std::min(a, b); } //combination(Nが小さい時はこれを使う const int MAX = 2330000; int fac[MAX], finv[MAX], inv[MAX]; // テーブルを作る前処理 void COMinit() { fac[0] = fac[1] = 1; finv[0] = finv[1] = 1; inv[1] = 1; for (int i = 2; i < MAX; i++) { fac[i] = fac[i - 1] * i % mod; inv[i] = mod - inv[mod % i] * (mod / i) % mod; finv[i] = finv[i - 1] * inv[i] % mod; } } int COMB(int n, int k) { if (n < k) return 0; if (n < 0 || k < 0) return 0; return fac[n] * (finv[k] * finv[n - k] % mod) % mod; } bool prime(int n) { int cnt = 0; for (int i = 1; i <= sqrt(n); i++) { if (n % i == 0)cnt++; } if (cnt != 1)return false; else return n != 1; } int gcd(int x, int y) { if (y == 0)return x; return gcd(y, x % y); } int lcm(int x, int y) { return x / gcd(x, y) * y; } //繰り返し二乗法(Nが大きい時の場合のcombination) int mod_pow(int x, int y, int m) { int res = 1; while (y) { if (y & 1) { res = res * x % m; } x = x * x % m; y >>= 1; } return res; } int kai(int x, int y) { int res = 1; for (int i = x - y + 1; i <= x; i++) { res *= (i % mod); res %= mod; } return res; } int comb(int x, int y) { if (y > x)return 0; return kai(x, y) * mod_pow(kai(y, y), mod - 2, mod) % mod; } //UnionFind class UnionFind { protected: int* par, * rank, * size; public: UnionFind(unsigned int size) { par = new int[size]; rank = new int[size]; this->size = new int[size]; rep(i, size) { par[i] = i; rank[i] = 0; this->size[i] = 1; } } int find(int n) { if (par[n] == n)return n; return par[n] = find(par[n]); } void unite(int n, int m) { n = find(n); m = find(m); if (n == m)return; if (rank[n] < rank[m]) { par[n] = m; size[m] += size[n]; } else { par[m] = n; size[n] += size[m]; if (rank[n] == rank[m])rank[n]++; } } bool same(int n, int m) { return find(n) == find(m); } int getsize(int n) { return size[find(n)]; } }; int dight(int n) { int ans = 1; while (n >= 10) { n /= 10; ans++; } return ans; } int dight_sum(int n) { int sum = 0; rep(i, 20)sum += (n % (int)pow(10, i + 1)) / (pow(10, i)); return sum; } int dight_min(int n) { int ans = 9; while (n >= 10) { ans = min(ans, n % 10); n /= 10; } ans = min(ans, n); return ans; } int dight_max(int n) { int ans = 0; while (n >= 10) { ans = max(ans, n % 10); n /= 10; } ans = max(ans, n); return ans; } long long modinv(long long a, long long m) { long long b = m, u = 1, v = 0; while (b) { long long t = a / b; a -= t * b; swap(a, b); u -= t * v; swap(u, v); } u %= m; if (u < 0) u += m; return u; } int n, m, a, b; signed main() { COMinit(); cin >> n >> m >> a >> b; if (a * (n - 1) > b) { cout << 0 << endl; ggr } int memo = 1; for (int i = 1; i <= n; i++) { memo *= i; memo %= mod; } int ans = 0; for (int i = 0; i <= b - a * (n - 1); i++) { int p = (m - a * (n - 1) - i) % mod; ans += (p * COMB(i + n - 2, i)) % mod; ans %= mod; } cout << ans * memo % mod << endl; ggr }