import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.StringTokenizer;
import java.util.TreeMap;
import java.util.concurrent.ConcurrentHashMap;

public class Main {
public static void main(String[] args){

   new Thread(null, null, "Anshum Gupta", 99999999) {
        public void run() {
            try {
                solve();
            } catch(Exception e) {
                e.printStackTrace();
                System.exit(1);
            }
        }
    }.start();
}
static final long mxx = (long)(1e18+5);
static final int mxN = (int)(1e6);
static final int mxV = (int)(1e6), log = 18;
static long mod = 998244353;//̇(long)(1e9+7); //
static final int INF = (int)1e9;
static boolean[]vis, recst;
static ArrayList<HashSet<Integer>> adj;
static int n, m, k, q, x , a, b, c, d;
static char[]str;
static char[][] arr;
static Long[][]dp;
public static void solve() throws Exception {
	   // solve the problem here
		s = new MyScanner();
   		out = new PrintWriter(new BufferedOutputStream(System.out), true);
//	   		out = new PrintWriter("output.txt");
        int tc = 1;//s.nextInt();
        for(int i=1; i<=tc; i++) {
//        	out.print("Case #" + i + ": ");
        	testcase();
        	
        }
           
        out.flush();
        out.close();
}
static long rec(int i, int j) {
	if(i > c || j > d) {
		return 0;
	}
	if(i == c && j == d)return 1;
	if(dp[i][j] != null)return dp[i][j];
	long ans = (rec(i+1, j) * (j))%mod + (rec(i, j+1) * (i))%mod - (rec(i+1, j+1) * i * j)%mod;
	ans = (ans + mod) % mod;
	return dp[i][j] = ans;
}
static void testcase() {
	a = s.nextInt(); b = s.nextInt(); c = s.nextInt(); d = s.nextInt();
	dp = new Long[c+1][d+1];
	long ans = rec(a, b);
	out.println(ans);
}

private static int gcd(int a, int b) {
	return b == 0 ? a : gcd(b, a%b);
}
public static PrintWriter out;
public static MyScanner s;
static class MyScanner {

    BufferedReader br;
    StringTokenizer st;

    public MyScanner() {
        br = new BufferedReader(new InputStreamReader(System.in));
    }
    public MyScanner(String fileName) {
    	try {
			br = new BufferedReader(new FileReader(fileName));
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		}
    }
    String next() {
        while (st == null || !st.hasMoreElements()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }

    int nextInt() { return Integer.parseInt(next()); }
    long nextLong() { return Long.parseLong(next()); }
    double nextDouble() { return Double.parseDouble(next()); }
    int[] nextIntArray(int n){
    	int[]a = new int[n];
    	for(int i=0; i<n; i++) {
    		a[i] = this.nextInt();
    	}
    	return a;
    }
    long[] nextlongArray(int n) {
    	long[]a = new long[n];
    	for(int i=0; i<n; i++) {
    		a[i] = this.nextLong();
    	}
    	return a;
    }
    Integer[] nextIntegerArray(int n){
    	Integer[]a = new Integer[n];
    	for(int i=0; i<n; i++) {
    		a[i] = this.nextInt();
    	}
    	return a;
    }
    Long[] nextLongArray(int n) {
    	Long[]a = new Long[n];
    	for(int i=0; i<n; i++) {
    		a[i] = this.nextLong();
    	}
    	return a;
    }
    char[][] next2DCharArray(int n, int m){
    	char[][]arr = new char[n][m];
    	for(int i=0; i<n; i++) {
    		arr[i] = this.next().toCharArray();
    	}
    	return arr;
    }
    ArrayList<ArrayList<Integer>> readUndirectedUnweightedGraph(int n, int m) {
    	ArrayList<ArrayList<Integer>>adj = new ArrayList<ArrayList<Integer>>();
    	for(int i=0; i<=n; i++)adj.add(new ArrayList<Integer>());
    	for(int i=0; i<m; i++) {
    		int u = s.nextInt();
    		int v = s.nextInt();
    		adj.get(u).add(v);
    		adj.get(v).add(u);
    	}
    	return adj;
    }
    ArrayList<ArrayList<Integer>> readDirectedUnweightedGraph(int n, int m) {
    	ArrayList<ArrayList<Integer>>adj = new ArrayList<ArrayList<Integer>>();
    	for(int i=0; i<=n; i++)adj.add(new ArrayList<Integer>());
    	for(int i=0; i<m; i++) {
    		int u = s.nextInt();
    		int v = s.nextInt();
    		adj.get(u).add(v);
    	}
    	return adj;
    }
    String nextLine(){
        String str = "";
        try {
            str = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return str;
    }
}

 
}


Measured memory_bytes: 381048