// #define DEBUG_IS_VALID #ifdef DEBUG_IS_VALID #define DEB 1 #define _LIBCPP_DEBUG 0 #else #define DEB 0 #define NDEBUG #endif #include "bits/stdc++.h" #define ALL(g) (g).begin(),(g).end() #define REP(i, x, n) for(int i = x; i < n; i++) #define rep(i,n) REP(i,0,n) #define RREP(i, x, n) for(int i = x; i >= n; i--) #define rrep(i, n) RREP(i,n,0) #define pb push_back #pragma GCC optimize ("-O3") using namespace std; #define DUMPOUT cout #define dump(...) if(DEB) DUMPOUT<<" "<<#__VA_ARGS__<<" :["<<__LINE__<<":"<<__FUNCTION__<<"]"<ostream& operator << (ostream& os, pair p){cout << "(" << p.first << ", " << p.second << ")"; return os;} templateostream& operator << (ostream& os, vector& vec) { os << "{"; for (int i = 0; iostream& operator << (ostream& os, set& st){cout << "{"; for(auto itr = st.begin(); itr != st.end(); itr++) cout << *itr << (next(itr)!=st.end() ? ", " : ""); cout << "}"; return os;} templateostream& operator << (ostream& os, map mp){cout << "{"; for(auto itr = mp.begin(); itr != mp.end(); itr++) cout << "(" << (itr->first) << ", " << (itr->second) << ")" << (next(itr)!=mp.end() ? "," : ""); cout << "}"; return os; } void dump_func(){DUMPOUT << endl;} template void dump_func(Head&& head, Tail&&... tail){ DUMPOUT << head; if (sizeof...(Tail) == 0) { DUMPOUT << " "; } else { DUMPOUT << ", "; } dump_func(std::move(tail)...);} template inline bool chmax(T& a,T const& b){if(a>=b) return false; a=b; return true;} template inline bool chmin(T& a,T const& b){if(a<=b) return false; a=b; return true;} void _main(); int main(){ cin.tie(0); ios::sync_with_stdio(false); _main(); return 0;} using ll = long long; using P = pair; using Pl = pair; using vi = vector; using vvi = vector; using vl = vector; using vvl = vector; const int mod=1e9+7,INF=1<<29; const double EPS=1e-5,PI=3.1415926535897932384626; const ll lmod = 1e9+7,LINF=1LL<<59; template struct ModInt { static const int Mod = MOD; unsigned x; ModInt() : x(0) { } ModInt(signed sig) { x = sig < 0 ? sig % MOD + MOD : sig % MOD; } ModInt(signed long long sig) { x = sig < 0 ? sig % MOD + MOD : sig % MOD; } int get() const { return (int)x; } ModInt &operator+=(ModInt that) { if ((x += that.x) >= MOD) x -= MOD; return *this; } ModInt &operator-=(ModInt that) { if ((x += MOD - that.x) >= MOD) x -= MOD; return *this; } ModInt &operator*=(ModInt that) { x = (unsigned long long)x * that.x % MOD; return *this; } ModInt &operator/=(ModInt that) { return *this *= that.inverse(); } ModInt operator+(ModInt that) const { return ModInt(*this) += that; } ModInt operator-(ModInt that) const { return ModInt(*this) -= that; } ModInt operator*(ModInt that) const { return ModInt(*this) *= that; } ModInt operator/(ModInt that) const { return ModInt(*this) /= that; } ModInt inverse() const { long long a = x, b = MOD, u = 1, v = 0; while (b) { long long t = a / b; a -= t * b; std::swap(a, b); u -= t * v; std::swap(u, v); } return ModInt(u); } bool operator==(ModInt that) const { return x == that.x; } bool operator!=(ModInt that) const { return x != that.x; } ModInt operator-() const { ModInt t; t.x = x == 0 ? 0 : Mod - x; return t; } }; template ostream& operator<<(ostream& st, const ModInt a) { st << a.get(); return st; }; template ModInt operator^(ModInt a, unsigned long long k) { ModInt r = 1; while (k) { if (k & 1) r *= a; a *= a; k >>= 1; } return r; } template struct Comb { vector fac, ifac; Comb(){fac.resize(FAC_MAX,1);ifac.resize(FAC_MAX,1); for(int i = 1; i < FAC_MAX; i++)fac[i]=fac[i-1]*i; ifac[FAC_MAX-1]=T(1)/fac[FAC_MAX-1];for(int i = FAC_MAX-2; i >= 1; i--)ifac[i]=ifac[i+1]*T(i+1);} T aPb(int a, int b) { if (b < 0 || a < b) return T(0); return fac[a] * ifac[a - b]; } T aCb(int a, int b) { if (b < 0 || a < b) return T(0); return fac[a] * ifac[a - b] * ifac[b]; } T nHk(int n, int k) { if (n == 0 && k == 0) return T(1); if (n <= 0 || k < 0) return 0; return aCb(n + k - 1, k); }}; // nHk = (n+k-1)Ck : n is separator using mint = ModInt; using vm = vector; map enumpr(ll n) { map V; for (ll i = 2; 1LL * i*i <= n; i++) while (n%i == 0) V[i]++, n /= i; if (n>1) V[n]++; return V; } Comb com; void _main(){ ll N,M,D1,D2; cin >> N >> M >> D1 >> D2 ; ll D = D2-D1; mint ans(0); rep(i,N+1){ int k = D1*(N-1-i)+(D2+1)*i+1; if(M-k<0) continue; ans += com.aCb(N-1,i) * mint(i%2==0?1:-1) * com.aCb(N+M-k,N); } cout << ans << endl; }