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

#include <iostream>
#include <fstream>

#ifndef  _TB
#define _TB

#include <bits/stdc++.h>

using namespace std;

#define FOR(i, a, b) for(int i = (a); i < (b); ++i)
#define RFOR(i, b, a) for(int i = (b) - 1; i >= (a); --i)
#define REP(i, N) FOR(i, 0, N)
#define RREP(i, N) RFOR(i, N, 0)

#define MIN(A, B) ((A) < (B) ? (A) : (B))
#define MAX(A, B) ((A) > (B) ? (A) : (B))
#define ABS(A) ((A) < 0 ? (-(A)) : (A))
#define ALL(V) V.begin(), V.end()
#define SIZE(V) (int)V.size()
#define pb push_back
#define mp make_pair
#define EPS 1e-7
#define Pi 3.14159265358979
#define FILL(a,v) memset(a,v,sizeof(a))

using namespace std;

typedef long long Long;
typedef unsigned long long ULong;
typedef unsigned int Uint;
typedef unsigned char Uchar;
typedef vector <int> VI;
typedef pair <int, int> PII;

#define X first
#define Y second

typedef std::pair<int,int> pii; typedef long long ll; typedef unsigned long long ull; typedef unsigned int ui; typedef pair<ui,ui> puu;

template <typename T, typename U> std::istream&operator>>(std::istream&i, pair<T,U>&p) {i >> p.X >> p.Y; return i;}
template<typename T>std::istream&operator>>(std::istream&i,vector<T>&t) {for(auto&v:t){i>>v;}return i;}
template <typename T, typename U> std::ostream&operator<<(std::ostream&o, const pair<T,U>&p) {o << p.X << ' ' << p.Y; return o;}
template<typename T>std::ostream&operator<<(std::ostream&o,const vector<T>&t) {if(t.empty())o<<'\n';for(size_t i=0;i<t.size();++i){o<<t[i]<<" \n"[i == t.size()-1];}return o;}
template<typename T> using minheap = priority_queue<T, vector<T>, greater<T>>;
template<typename T> using maxheap = priority_queue<T, vector<T>, less<T>>;
template <typename T> bool in(T a, T b, T c) { return a <= b && b < c; }
ui logceil(int x) { return (ui)(8*sizeof(int)-__builtin_clz(x)); }

namespace std { template<typename T,typename U>struct hash<pair<T,U>>{hash<T>t;hash<U>u;size_t operator()(const pair<T,U>&p)const{return t(p.x)^(u(p.y)<<7);}}; }
template<typename T> T gcd(T a,T b) { if (a<b) swap(a,b); return b?gcd(b,a%b):a; }

template<typename T>class vector2:public vector<vector<T>>{public:vector2(){} vector2(size_t a,size_t b,T t=T()):vector<vector<T>>(a,vector<T>(b,t)){}};
template<typename T>class vector3:public vector<vector2<T>>{public:vector3(){} vector3(size_t a,size_t b,size_t c,T t=T()):vector<vector2<T>>(a,vector2<T>(b,c,t)){}};
template<typename T>class vector4:public vector<vector3<T>>{public:vector4(){} vector4(size_t a,size_t b,size_t c,size_t d,T t=T()):vector<vector3<T>>(a,vector3<T>(b,c,d,t)){}};
template<typename T>class vector5:public vector<vector4<T>>{public:vector5(){} vector5(size_t a,size_t b,size_t c,size_t d,size_t e,T t=T()):vector<vector4<T>>(a,vector4<T>(b,c,d,e,t)){}};

void fastIO(){ios::sync_with_stdio(false); }

#endif
#ifndef MOD_H
#define MOD_H




template <unsigned int N> class Field {
    typedef unsigned int ui;
    typedef unsigned long long ull;
    inline ui pow(ui a, ui p){ui r=1,e=a;while(p){if(p&1){r=((ull)r*e)%N;}e=((ull)e*e)%N;p>>=1;}return r;}
    /*extended GCD(slow):ll t=0,nt=1,r=N,nr=a;while(nr){ll q=r/nr;t-=q*nt;swap(t,nt);r-=q*nr;swap(r,nr);}assert(r<=1);return(t<0)?t+N:t;*/
    inline ui inv(ui a){return pow(a,N-2);}
public:
    inline Field(Long x = 0) : v((ui)(x%N)) {}
    inline Field<N> pow(int p){return (*this)^p; }
    inline Field<N> operator^(int p){return {(int)pow(v,(ui)p)};}
    inline Field<N>&operator+=(const Field<N>&o) {if ((ll)v+o.v >= N) v += o.v - N; else v += o.v; return *this; }
    inline Field<N>&operator-=(const Field<N>&o) {if (v<o.v) v -= o.v-N; else v-=o.v; return *this; }
    inline Field<N>&operator*=(const Field<N>&o) {v=(ui)((ull)v*o.v % N); return *this; }
    inline Field<N>&operator/=(const Field<N>&o) { return *this*=inv(o.v); }
    inline Field<N> operator+(const Field<N>&o) const {Field<N>r{*this};return r+=o;}
    inline Field<N> operator-(const Field<N>&o) const {Field<N>r{*this};return r-=o;}
    inline Field<N> operator*(const Field<N>&o) const {Field<N>r{*this};return r*=o;}
    inline Field<N> operator/(const Field<N>&o) const {Field<N>r{*this};return r/=o;}
    inline Field<N> operator-() {if(v) return {(int)(N-v)}; else return {0};};
    inline Field<N>& operator++() { ++v; if (v==N) v=0; return *this; }
    inline Field<N> operator++(int) { Field<N>r{*this}; ++*this; return r; }
    inline Field<N>& operator--() { --v; if (v==-1) v=N-1; return *this; }
    inline Field<N> operator--(int) { Field<N>r{*this}; --*this; return r; }
    inline bool operator==(const Field<N>&o) const { return o.v==v; }
    inline bool operator!=(const Field<N>&o) const { return o.v!=v; }
    inline explicit operator ui() const { return v; }
    inline static vector<Field<N>>fact(int t){vector<Field<N>>F(t+1,1);for(int i=2;i<=t;++i){F[i]=F[i-1]*i;}return F;}
    inline static vector<Field<N>>invfact(int t){vector<Field<N>>F(t+1,1);Field<N> X{1};for(int i=2;i<=t;++i){X=X*i;}F[t]=1/X;for(int i=t-1;i>=2;--i){F[i]=F[i+1]*(i+1);}return F;}
private: ui v;
};
template<unsigned int N>istream &operator>>(std::istream&is,Field<N>&f){unsigned int v;is>>v;f=v;return is;}
template<unsigned int N>ostream &operator<<(std::ostream&os,const Field<N>&f){return os<<(unsigned int)f;}
template<unsigned int N>Field<N> operator+(int i,const Field<N>&f){return Field<N>(i)+f;}
template<unsigned int N>Field<N> operator-(int i,const Field<N>&f){return Field<N>(i)-f;}
template<unsigned int N>Field<N> operator*(int i,const Field<N>&f){return Field<N>(i)*f;}
template<unsigned int N>Field<N> operator/(int i,const Field<N>&f){return Field<N>(i)/f;}


typedef Field<1000000007> FieldMod;

struct Ring {
    static int div(int p, int q, int N) {
        ll t=0,nt=1,r=N,nr=q;
        while(nr){ ll qq=r/nr;t-=qq*nt;r-=qq*nr;swap(t,nt);swap(r,nr); }
        t=(t<0)?t+N:t;
        r=(r<0)?r+N:r;
        if (gcd(p,N)%r) { return 0; }
        return (int)(((ll)t*(ll)p/r)%N);
    }
};
#endif

const int MAXN = 3030;

Field<998244353> dp[MAXN+5][MAXN+5];

class BExtension {
public:
    void solve(std::istream& in, std::ostream& out) {
        // fastIO();
        FILL(dp, 0);
        int a,b,c,d;
        in >> a >> b >> c >> d;
        dp[a][b] = 1;
        REP(i, MAXN)
            REP(j, MAXN) {
            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() {
	BExtension solver;
	std::istream& in(std::cin);
	std::ostream& out(std::cout);
	solver.solve(in, out);
	cerr << 1.0 * clock() / CLOCKS_PER_SEC << endl;
	return 0;
}


Measured memory_bytes: 39768