#include <bits/stdc++.h>
using namespace std;

// template {{{
#define  range(i, l, r) for (int i = (int)(l); i < (int)(r); (i) += 1)
#define rrange(i, l, r) for (int i = (int)(r) - 1; i >= (int)(l); (i) -= 1)

#define  whole(f, x, ...) ([&](decltype((x)) container) { return (f)(  begin(container),  end(container), ## __VA_ARGS__); })(x)
#define rwhole(f, x, ...) ([&](decltype((x)) container) { return (f)( rbegin(container), rend(container), ## __VA_ARGS__); })(x)

#define debug(x) cerr << "(" << __LINE__ << ")" << #x << ": " << (x) << endl

using i32 = int;
using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;

constexpr i32 mod   = 998244353;
//constexpr i32 mod   = 1e9 + 7;
constexpr i32 inf   = 1001001001;
constexpr i64 infll = 1001001001001001001ll;

constexpr int dx[] = {0, -1, 1, 0, -1, 1, -1, 1};
constexpr int dy[] = {-1, 0, 0, 1, -1, -1, 1, 1};

struct IoSetup { IoSetup(int x = 15){ cin.tie(0); ios::sync_with_stdio(0); cout << fixed << setprecision(x); cerr << fixed << setprecision(x); } } iosetup;

template <typename T = i64> T input() { T x; cin >> x; return x; }

template <typename T> ostream &operator<<(ostream &os, vector<T> &v) { range(i, 0, v.size()) { os << v[i] << (i + 1 != v.size() ? " " : ""); } return os; }
template <typename T> istream &operator>>(istream &is, vector<T> &v) { for (T &in : v) is >> in; return is; }

template <typename T1, typename T2> ostream &operator<<(ostream &os, pair<T1, T2> p) { os << "(" << p.first << ", " << p.second << ")"; return os; }
template <typename T1, typename T2> istream &operator>>(istream &is, pair<T1, T2> &p) { is >> p.first >> p.second; return is; }

template <typename T> vector<T> make_vector(size_t a, T b) { return vector<T>(a, b); }
template <typename... Ts> auto make_vector(size_t a, Ts... ts) { return vector<decltype(make_vector(ts...))>(a, make_vector(ts...)); }

template <typename T1, typename T2> inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
template <typename T1, typename T2> inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }
// }}}

// mod_int {{{
template < int mod >
class mod_int {
    using i32 = int_fast32_t;
    using i64 = int_fast64_t;

    i32 num_;

    public:
    mod_int() : num_(0) {}
    mod_int(i64 num_) : num_(num_ >= 0 ? num_ % mod : (mod + num_ % mod) % mod) {}

    inline i32 num() const { return num_; }
    operator i32() { return num_; }

    inline mod_int inverse() const {
        i32 a = num_, b = mod, u = 1, v = 0, t;
        while (b) { t = a / b; std::swap(a -= t * b, b); std::swap(u -= t * v, v); }
        return mod_int(u);
    }

    mod_int operator~() const { return inverse(); }
    mod_int operator+() const { return *this; }
    mod_int operator-() const { return mod_int(-num_); }

    mod_int &operator+=(const mod_int &rhs) { if ((num_ += rhs.num_) >= mod) num_ -= mod; return *this; }
    mod_int &operator-=(const mod_int &rhs) { if ((num_ -= rhs.num_) <  0)   num_ += mod; return *this; }
    mod_int &operator*=(const mod_int &rhs) { num_ = i64(num_) * rhs.num_ % mod; return *this; }
    mod_int &operator/=(const mod_int &rhs) { return *this *= rhs.inverse(); }

    mod_int operator+(const mod_int &rhs) const { return mod_int(*this) += rhs; }
    mod_int operator-(const mod_int &rhs) const { return mod_int(*this) -= rhs; }
    mod_int operator*(const mod_int &rhs) const { return mod_int(*this) *= rhs; }
    mod_int operator/(const mod_int &rhs) const { return mod_int(*this) /= rhs; }

    bool operator==(const mod_int &rhs) const { return num_ == rhs.num_; }
    bool operator!=(const mod_int &rhs) const { return num_ != rhs.num_; }

    friend std::ostream &operator<<(std::ostream &os, const mod_int &rhs) {
        return os << rhs.num_;
    }

    friend std::istream &operator>>(std::istream &is, mod_int &rhs) {
        i64 num; is >> num; rhs = mod_int< mod >(num);
        return is;
    }

    friend mod_int pow(mod_int lhs, i64 rhs) {
        mod_int res(1);
        for (; rhs; rhs >>= 1) {
            if (rhs & 1) res *= lhs;
            lhs *= lhs;
        }
        return res;
    }
};
// }}}

using modint = mod_int< mod >;

void solver() {
    int a, b, c, d;
    cin >> a >> b >> c >> d;

    auto dp = make_vector(c + 2, d + 2, modint(0));
    dp[a][b] = 1;
    range(i, a, c + 1) range(j, b, d + 1) {
        dp[i + 1][j] += modint(j) * dp[i][j];
        dp[i][j + 1] += modint(i) * dp[i][j];
        dp[i + 1][j + 1] -= modint(i * j) * dp[i][j];
    }

    cout << dp[c][d] << endl;
}

signed main(int argc, char *argv[]) {
    solver();
} 


Measured memory_bytes: 73680