#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef unsigned long long ull;
typedef long double ld;
int dx[8] = { 1, 0, -1, 0, 1, 1, -1, -1 }, dy[8] = { 0, 1, 0, -1, 1, -1, 1, -1 };
const long long mod = 998244353;
const ll inf = 1LL << 60;
const int INF = 5e8;

template <int MOD>
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 <int MOD>
ostream& operator<<(ostream& st, const ModInt<MOD> a)
{
    st << a.get();
    return st;
};
template <int MOD>
ModInt<MOD> operator^(ModInt<MOD> a, unsigned long long k)
{
    ModInt<MOD> r = 1;
    while (k) {
        if (k & 1)
            r *= a;
        a *= a;
        k >>= 1;
    }
    return r;
}

template <typename T, int FAC_MAX>
struct Comb {
    vector<T> 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);
    }
};
typedef ModInt<998244353> mint;
Comb<mint, 2000009> comb;

int main()
{
    int x, y, z, w;
    cin >> x >> y >> z >> w;

    int a = x - z;
    int b = y - w;

    mint ans = comb.aPb(x, a) * comb.aPb(y, b);
    if (z == 0)
        ans *= comb.aCb(a + b - 1, b);
    else
        ans *= comb.aCb(a + b - 1, a);

    cout << ans << endl;
}