//
//  main.cpp
//

#include <algorithm>
#include <array>
#include <assert.h>
#include <complex>
#include <iomanip>
#include <iostream>
#include <limits>
#include <map>
#include <math.h>
#include <memory>
#include <memory>
#include <queue>
#include <random>
#include <set>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std;

using ll = int64_t;
using ull = uint64_t;

[[maybe_unused]] constexpr ll LL_MAX = numeric_limits<ll>::max();
[[maybe_unused]] constexpr ll LL_MIN = numeric_limits<ll>::min();
[[maybe_unused]] constexpr ull ULL_MAX = numeric_limits<ull>::max();

#define rep(i, a, b) for (ll i = (a); i < (b); i++)
#define rrep(i, a, b) for (ll i = (a)-1; i >= (b); i--)

template <typename T>
void chmin(T& x, T y) {
    x = min(x, y);
}

template <typename T>
void chmax(T& x, T y) {
    x = max(x, y);
}

ll csum(ll x, ll y) {
    if (x > 0 && y > 0 && x > LL_MAX - y) {
        return LL_MAX;
    }
    if (x < 0 && y < 0 && x < LL_MIN - y) {
        return LL_MIN;
    }
    return x + y;
}

template<typename T>
vector<T> make_vec_nd(T init, ll size) {
	return vector<T>(size, init);
}
template<typename T, typename... Args>
auto make_vec_nd(T init, ll size, Args... rest) {
	auto inner = make_vec_nd(init, rest...);
	return vector<decltype(inner)>(size, inner);
}

struct Mod {
    static uint64_t PRIME;
    struct LocalPrime {
        uint64_t backup;
        LocalPrime(uint64_t prime) { backup = exchange(Mod::PRIME, prime); }
        ~LocalPrime() { Mod::PRIME = backup; }
    };
    uint64_t value = 0;
    Mod()
    : value(0) {}
    Mod(ll v) {
        if (v >= 0) {
            value = v % PRIME;
        } else {
            value = PRIME - (-v) % PRIME;
        }
    }
    Mod operator+(const Mod& rhs) const { return Mod(*this) += rhs; }
    Mod& operator+=(const Mod& rhs) {
        value += rhs.value;
        if (value >= PRIME) {
            value -= PRIME;
        }
        return *this;
    }
    Mod operator-(const Mod& rhs) const { return Mod(*this) -= rhs; }
    Mod& operator-=(const Mod& rhs) {
        if (value < rhs.value) {
            value += PRIME;
        }
        value -= rhs.value;
        return *this;
    }
    Mod operator*(const Mod& rhs) const { return Mod(*this) *= rhs; }
    Mod& operator*=(const Mod& rhs) {
        value = (value * rhs.value) % PRIME;
        return *this;
    }
    Mod inv() const { return power(*this, PRIME - 2); }
    Mod operator/(const Mod& rhs) const { return Mod(*this) /= rhs; }
    Mod& operator/=(const Mod& rhs) {
        *this *= rhs.inv();
        return *this;
    }
    static Mod power(Mod rhs, ll exp) {
        Mod ans = 1;
        while (exp > 0) {
            if (exp % 2) {
                ans *= rhs;
            }
            rhs *= rhs;
            exp /= 2;
        }
        return ans;
    }
};
uint64_t Mod::PRIME = 998244353;

int main() {
    ll A, B, C, D;
    cin >> A >> B >> C >> D;
    auto dp = make_vec_nd((Mod)0, C-A+1, D-B+1);
    rep(x,0,C-A+1) {
        rep(y,0,D-B+1) {
            if (x == 0 || y == 0) {
                dp[x][y] = Mod::power(A, y) * Mod::power(B, x);
                continue;
            }
            dp[x][y] += dp[x][y-1] * (A + x);
            dp[x][y] += dp[x-1][y] * (B + y);
            dp[x][y] -= dp[x-1][y-1] * (A + x - 1) * (B + y - 1);
        }
    }
    cout << dp[C-A][D-B].value << endl;
}

/*
 
 1 1 2 3
 
 */


Measured memory_bytes: 73368