#include <bits/stdc++.h>
//#include <boost/multiprecision/cpp_int.hpp>
//namespace mp = boost::multiprecision;

using namespace std;

const double PI = 3.14159265358979323846;
typedef long long ll;
const double EPS = 1e-9;
#define rep(i, n) for (int i = 0; i < (n); ++i)
//#define rep(i, n) for (ll i = 0; i < (n); ++i)
typedef pair<ll, ll> P;
const ll INF = 10e17;
#define cmin(x, y) x = min(x, y)
#define cmax(x, y) x = max(x, y)
#define ret() return 0;

double equal(double a, double b) {
    return fabs(a - b) < DBL_EPSILON;
}

std::istream &operator>>(std::istream &in, set<int> &o) {
    int a;
    in >> a;
    o.insert(a);
    return in;
}

std::istream &operator>>(std::istream &in, queue<int> &o) {
    ll a;
    in >> a;
    o.push(a);
    return in;
}

bool contain(set<int> &s, int a) { return s.find(a) != s.end(); }

//ofstream outfile("log.txt");
//outfile << setw(6) << setfill('0') << prefecture << setw(6) << setfill('0') << rank << endl;
// std::cout << std::bitset<8>(9);
//const ll mod = 1e10;

typedef priority_queue<ll, vector<ll>, greater<ll> > PQ_ASK;

const int mod = 998244353;

struct mint {
    ll x; // typedef long long ll;
    mint(ll x = 0) : x((x % mod + mod) % mod) {}

    mint &operator+=(const mint a) {
        if ((x += a.x) >= mod) x -= mod;
        return *this;
    }

    mint &operator-=(const mint a) {
        if ((x += mod - a.x) >= mod) x -= mod;
        return *this;
    }

    mint &operator*=(const mint a) {
        (x *= a.x) %= mod;
        return *this;
    }

    mint operator+(const mint a) const {
        mint res(*this);
        return res += a;
    }

    mint operator-(const mint a) const {
        mint res(*this);
        return res -= a;
    }

    mint operator*(const mint a) const {
        mint res(*this);
        return res *= a;
    }

    mint pow(ll t) const {
        if (!t) return 1;
        mint a = pow(t >> 1);
        a *= a;
        if (t & 1) a *= *this;
        return a;
    }

    // for prime mod
    mint inv() const {
        return pow(mod - 2);
    }

    mint &operator/=(const mint a) {
        return (*this) *= a.inv();
    }

    mint operator/(const mint a) const {
        mint res(*this);
        return res /= a;
    }

    friend std::istream &operator>>(std::istream &in, mint &o) {
        ll a;
        in >> a;
        o = a;
        return in;
    }

    friend std::ostream &operator<<(std::ostream &out, const mint &o) {
        out << o.x;
        return out;
    }

};


void print(vector<vector<mint>> &dp) {
    for (auto &l : dp) {
        for (mint f : l) cout << f << ' ';
        cout << endl;
    }
}

int main() {

    int sh, sw, eh, ew;
    cin >> sh >> sw >> eh >> ew;

    sh--;
    sw--;
    eh--;
    ew--;


    vector<vector<mint>> dp(eh + 1, vector<mint>(ew + 1, 0));


    for (int y = 0; y <= eh; y++) {
        for (int x = 0; x <= ew; x++) {
            mint next = [&]() -> mint {
                if (y < sh || x < sw) return 0;
                if (y <= sh && x <= sw) return 1;
                if (y == sh) return dp[y][x - 1] * (y + 1);
                if (x == sw) return dp[y - 1][x] * (x + 1);
                // [2][1] * 2
                mint v = dp[y - 1][x] * (x + 1);
                mint h = dp[y][x - 1] * (y + 1);
                mint d = dp[y - 1][x - 1] * y * x;

                return v + h - d;

            }();
            dp[y][x] = next;
        }
    }

//    print(dp);
    cout << dp[eh][ew] << endl;
}


Measured memory_bytes: 73684