#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#ifdef tabr
#include "library/debug.cpp"
#else
#define debug(...)
#endif

template <long long mod>
struct modular {
    long long value;
    modular(long long x = 0) {
        value = x % mod;
        if (value < 0) value += mod;
    }
    modular& operator+=(modular other) {
        if ((value += other.value) >= mod) value -= mod;
        return *this;
    }
    modular& operator-=(modular other) {
        if ((value -= other.value) < 0) value += mod;
        return *this;
    }
    modular& operator*=(modular other) {
        value = value * other.value % mod;
        return *this;
    }
    modular& operator/=(modular other) {
        long long a = 0, b = 1, c = other.value, m = mod;
        while (c != 0) {
            long long t = m / c;
            m -= t * c;
            swap(c, m);
            a -= t * b;
            swap(a, b);
        }
        a %= mod;
        if (a < 0) a += mod;
        value = value * a % mod;
        return *this;
    }
    modular operator-() { return modular(-value); }
    modular operator+(modular rhs) { return modular(*this) += rhs; }
    modular operator-(modular rhs) { return modular(*this) -= rhs; }
    modular operator*(modular rhs) { return modular(*this) *= rhs; }
    modular operator/(modular rhs) { return modular(*this) /= rhs; }
    bool operator==(modular rhs) { return value == rhs.value; }
    bool operator!=(modular rhs) { return value != rhs.value; }
    bool operator<(modular rhs) { return value < rhs.value; }
};
template <long long mod>
string to_string(modular<mod> x) {
    return to_string(x.value);
}
template <long long mod>
ostream& operator<<(ostream& stream, modular<mod> x) {
    x.value %= mod;
    if (x.value < 0) x.value += mod;
    return stream << x.value;
}
template <long long mod>
istream& operator>>(istream& stream, modular<mod>& x) {
    stream >> x.value;
    x.value %= mod;
    if (x.value < 0) x.value += mod;
    return stream;
};
const long long mod = 998244353LL;
using mint = modular<mod>;

inline mint pw(mint a, long long n) {
    mint res = 1;
    while (n > 0) {
        if (n & 1) {
            res *= a;
        }
        a *= a;
        n >>= 1;
    }
    return res;
}
vector<mint> fact, finv;
inline void cinit(int n) {
    fact.resize(n, 1);
    finv.resize(n, 1);
    for (int i = 2; i < n; i++) {
        fact[i] = fact[i - 1] * i;
    }
    finv[n - 1] /= fact[n - 1];
    for (int i = n - 2; i >= 2; i--) {
        finv[i] = finv[i + 1] * (i + 1);
    }
}
inline mint C(int n, int k) {
    if (n < k || k < 0 || n < 0) return 0;
    return fact[n] * finv[k] * finv[n - k];
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int a, b, c, d;
    cin >> a >> b >> c >> d;
    vector<vector<mint>> dp(c - a + 1, vector<mint>(d - b + 1));
    dp[0][0] = 1;
    for (int i = 0; i < c - a + 1; i++) {
        for (int j = 0; j < d - b + 1; j++) {
            if (i) {
                dp[i][j] += dp[i - 1][j] * (b + j);
            }
            if (j) {
                dp[i][j] += dp[i][j - 1] * (a + i);
            }
            if (i && j) {
                dp[i][j] -= dp[i - 1][j - 1] * (a + i - 1) * (b + j - 1);
            }
        }
    }
    debug(dp);
    cout << dp[c - a][d - b] << '\n';
    return 0;
}

Measured memory_bytes: 73652