/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author champon
 */

//<editor-fold desc="definitions">
#include <bits/stdc++.h>
#define se cout << "test ok" << endl;
#define sp << " " <<
#define enl "\n"
using namespace std;
using ll=long long;
using ld=long double;
using vi = vector<int>;
using vii = vector<vector<int>>;
using viii = vector<vector<vector<int>>>;
using vl = vector<ll>;
using vll = vector<vector<ll>>;
using vlll = vector<vector<vector<ll>>>;
using vc = vector<char>;
using vcc = vector<vector<char>>;
using pi = pair<int, int>;
using pl = pair<ll, ll>;
ll mod = ll(1e9)+7;
ll inf = ll(1e18);
void bl(bool b, ostream& out=cout){ out << (b ? "Yes" : "No") << endl; }
void bl2(bool b, ostream& out=cout){ out << (b ? "YES" : "NO") << endl; }
template<typename T> inline bool chmax(T &a, T b){ if(a<b){a=b; return true;} return false; }
template<typename T> inline bool chmin(T &a, T b){ if(a>b){a=b; return true;} return false; }
int dx[] = {1, 0, -1, 0, 1, -1, 1, -1};
int dy[] = {0, 1, 0, -1, 1, -1, -1, 1};

#ifndef INCLUDE_DEBUG_HPP
#define INCLUDE_DEBUG_HPP

#define TO_STRING(varName) # varName
#include <iostream>
#include <vector>
#include <map>
using namespace std;

namespace dbg {

using ll = long long;

class Debug {
  void prefix() { cout << "\033[7m\033[35m" << " DEBUG " << "\033[0m" << endl; }

  void out_helper(){ cout << endl; }

  void out_with_name_helper(){ cout << endl; }

  template<typename T1, typename... T2>
  void out_helper(T1 v, T2... args);

  template<typename T1, typename... T2>
  void out_with_name_helper(string s, T1 v, T2... args);

  // value
  template<typename T>
  void print(T val);

  // pair
  template<typename A, typename B>
  void print(pair<A, B> p);

  // tuple
  template<typename A, typename B, typename C>
  void print(tuple<A, B, C> t);

  // vector
  template<typename T>
  void print(vector<T> &vec);

  // set
  template<typename T>
  void print(set<T> &st);

  // map
  template<typename A, typename B>
  void print(map<A, B> mp);
public:
  Debug(){}

  template<typename... T>
  void out(T... args){
    prefix();
    out_helper(args...);
  }

  template<typename... T>
  void out_with_name(T... args){
    prefix();
    out_with_name_helper(args...);
  }

  template<typename T>
  void outg(vector<vector<T>> &g) {
    prefix();
    for(auto& v1 : g){
      for(auto& v2 : v1) {
        cout << v2 << " ";
      }
      cout << endl;
    }
  }
};

template<typename T1, typename... T2>
void Debug::out_helper(T1 v, T2... args) {
  print(v); cout << endl;
  out_helper(args...);
}

template<typename T1, typename... T2>
void Debug::out_with_name_helper(string s, T1 v, T2... args) {
  cout << s << ": "; print(v); cout << endl;
  out_with_name_helper(args...);
}

template<typename T>
void Debug::print(T val){
  cout << val;
}

template<typename A, typename B>
void Debug::print(pair<A, B> p){
  cout << "("; print(p.first); cout << ", "; print(p.second); cout << ")";
}

template<typename A, typename B, typename C>
void Debug::print(tuple<A, B, C> t) {
  cout << "("; print(get<0>(t)); cout << ", "; print(get<1>(t)); cout << ", "; print(get<2>(t)); cout << ")";
}

template<typename T>
void Debug::print(vector<T>& vec) {
  cout << "[";
  bool fir = true;
  for(auto& e : vec) {
    if(!fir) cout << " ";
    print(e), fir=false;
  }
  cout << "]";
}

template<typename T>
void Debug::print(set<T> &st){
  cout << "{";
  bool fir = true;
  for(auto& e : st) {
    if(!fir) cout << " ";
    print(e), fir=false;
  }
  cout << "}";
}

template<typename A, typename B>
void Debug::print(map<A, B> mp){
  cout << "{";
  bool fir = true;
  for(auto& p : mp){
    if(!fir) cout << " ";
    print(p), fir=false;
  }
  cout << "}";
}

}

#endif //INCLUDE_DEBUG_HPP

dbg::Debug debug;
//</editor-fold>

#ifndef INCLUDE_MINT_HPP
#define INCLUDE_MINT_HPP

#include <ostream>

namespace mint {

using ll = long long;

class Mint {
public:
  ll v;
  ll mod;

  Mint(ll v=0, ll mod=ll(1e9)+7) : mod(mod), v((v % mod + mod) % mod) {}

  friend std::ostream& operator<<(std::ostream& os, const Mint& val) {
    os << val.v;
    return os;
  }

  Mint operator-() const { return Mint(-v); }
  Mint operator+(const Mint rhs) const {
    Mint res(*this);
    return res += rhs;
  }
  Mint operator-(const Mint rhs) const {
    Mint res(*this);
    return res -= rhs;
  }
  Mint operator*(const Mint rhs) const {
    Mint res(*this);
    return res *= rhs;
  }
  Mint &operator+=(const Mint rhs) {
    if ((v += rhs.v) >= mod) v -= mod;
    return *this;
  }
  Mint &operator-=(const Mint rhs) {
    if ((v += mod - rhs.v) >= mod) v -= mod;
    return *this;
  }
  Mint &operator*=(const Mint rhs) {
    (v *= rhs.v) %= mod;
    return *this;
  }
  Mint pow(ll t) const {
    if (!t) return 1;
    Mint b = pow(t >> 1);
    b *= b;
    if (t & 1) b *= *this;
    return b;
  }
  Mint inv() const {
    return pow(mod - 2);
  }
  Mint &operator/=(const Mint rhs) {
    return (*this) *= rhs.inv();
  }
  Mint operator/(const Mint rhs) const {
    Mint res(*this);
    return res /= rhs;
  }
};

}

#endif //INCLUDE_MINT_HPP

using mint::Mint;

class BExtension {
public:
  void solve(std::istream& in, std::ostream& out){
    int a, b, c, d;
    in >> a >> b >> c >> d;

    mod = 998244353;
    vector<vector<Mint>> dp(c+2, vector<Mint>(d+2, Mint(0, mod)));
    dp[a][b] = 1;
    for(int i=a; i<=c; i++){
      for(int j=b; j<=d; j++){
        dp[i+1][j] += dp[i][j]*j;
        dp[i][j+1] += dp[i][j]*i;
        dp[i+1][j+1] -= dp[i][j]*i*j;
      }
    }

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


int main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  BExtension solver;
  std::istream& in(std::cin);
  std::ostream& out(std::cout);
  solver.solve(in, out);
  return 0;
}


Measured memory_bytes: 144020