#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <numeric>
#include <utility>
#include <tuple>

#define REP(i, a, b) for (int i = int(a); i < int(b); i++)
using namespace std;
using ll = long long int;
using P = pair<ll, ll>;

// clang-format off
#ifdef _DEBUG_
#define dump(...) do{ cerr << __LINE__ << ":\t" << #__VA_ARGS__ << " = "; PPPPP(__VA_ARGS__); cerr << endl; } while(false)
template<typename T> void PPPPP(T t) { cerr << t; }
template<typename T, typename... S> void PPPPP(T t, S... s) { cerr << t << ", "; PPPPP(s...); }
#else
#define dump(...) do{ } while(false)
#endif
template<typename T> vector<T> make_v(size_t a, T b) { return vector<T>(a, b); }
template<typename... Ts> auto make_v(size_t a, Ts... ts) { return vector<decltype(make_v(ts...))>(a, make_v(ts...)); }
template<typename T> bool chmin(T &a, T b) { if (a > b) {a = b; return true; } return false; }
template<typename T> bool chmax(T &a, T b) { if (a < b) {a = b; return true; } return false; }
template<typename T> void print(T a) { cout << a << endl; }
template<typename T, typename... Ts> void print(T a, Ts... ts) { cout << a << ' '; print(ts...); }
template<typename T> istream &operator,(istream &in, T &t) { return in >> t; }
// clang-format on

template<ll MOD = 1000000007>
class ModInt {
    ll n;
    ModInt constexpr inverse() const {
        return ModInt::pow(*this, MOD - 2);
    }

public:
    ModInt()
        : n(0) {}
    ModInt(ll _n)
        : n(((_n % MOD) + MOD) % MOD) {}
    ModInt operator+=(const ModInt &m) {
        n += m.n;
        if (n >= MOD) n -= MOD;
        return *this;
    }
    ModInt operator-=(const ModInt &m) {
        n -= m.n;
        if (n < 0) n += MOD;
        return *this;
    }
    ModInt operator*=(const ModInt &m) {
        n *= m.n;
        if (n >= MOD) n %= MOD;
        return *this;
    }
    ModInt operator/=(const ModInt &m) {
        (*this) *= m.inverse();
        return *this;
    }
    friend ModInt operator+(ModInt t, const ModInt &m) {
        return t += m;
    }
    friend ModInt operator-(ModInt t, const ModInt &m) {
        return t -= m;
    }
    friend ModInt operator*(ModInt t, const ModInt &m) {
        return t *= m;
    }
    friend ModInt operator/(ModInt t, const ModInt &m) {
        return t /= m;
    }
    ModInt operator=(const ll l) {
        n = l % MOD;
        if (n < 0) n += MOD;
        return *this;
    }
    friend ostream &operator<<(ostream &out, const ModInt &m) {
        out << m.n;
        return out;
    }
    friend istream &operator>>(istream &in, ModInt &m) {
        ll l;
        in >> l;
        m = l;
        return in;
    }
    static constexpr ModInt pow(const ModInt x, ll p) {
        ModInt<MOD> ans = 1;
        for (ModInt<MOD> m = x; p > 0; p /= 2, m *= m) {
            if (p % 2) ans *= m;
        }
        return ans;
    }
};
using mint = ModInt<998244353>;
mint operator"" _m(unsigned long long m) {
    return mint(m);
}

#include <array>
template<size_t N>
class INDEX {
    array<size_t, N> arr;

public:
    template<typename... T>
    INDEX(T... _arr)
        : arr({{static_cast<size_t>(_arr)...}}) {}
    template<typename... T>
    size_t operator()(T... _arr) {
        size_t position[] = {static_cast<size_t>(_arr)...};
        static_assert(N == size(position));
        size_t res = 0, width = 1;
        for (int i = N - 1; i >= 0; i--) {
            res += width * position[i];
            width *= arr[i];
        }
        return res;
    }
};
template<typename... T>
auto Index(T... args) {
    unsigned int arr[] = {static_cast<unsigned int>(args)...};
    constexpr size_t N = size(arr);
    return INDEX<N>(args...);
}
template<typename T, typename... Args>
auto make_v_flat(T init, Args... args) {
    return vector<T>((1 * ... * args), init);
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int a, b, c, d;
    cin, a, b, c, d;
    auto dp = make_v_flat(0_m, c - a + 1, d - b + 1);
    auto index = Index(c - a + 1, d - b + 1);
    dp[index(0, 0)] = 1;

    REP(i, 0, c - a + 1) {
        REP(j, 0, d - b + 1) {
            if (i > 0) {
                dp[index(i, j)] += (b + j) * dp[index(i - 1, j)];
            }
            if (j > 0) {
                dp[index(i, j)] += (a + i) * dp[index(i, j - 1)];
            }
            if (i > 0 && j > 0) {
                dp[index(i, j)] -= (b + j - 1) * (a + i - 1) * dp[index(i - 1, j - 1)];
            }
        }
    }

    print(dp[index(c - a, d - b)]);

    return 0;
}


Measured memory_bytes: 73372