import std.stdio, std.conv, std.string, std.array, std.range, std.algorithm, std.container;
import std.math, std.random, std.bigint, std.datetime, std.format;
void main(string[] args){ if(args.length > 1) if(args[1] == "-debug") DEBUG = 1; solve(); } bool DEBUG = 0; 
void log(A ...)(lazy A a){ if(DEBUG) print(a); }
void print(){ writeln(""); } void print(T)(T t){ writeln(t); } void print(T, A ...)(T t, A a){ write(t, " "), print(a); }
string unsplit(T)(T xs){ return xs.array.to!(string[]).join(" "); }
string scan(){ static string[] ss; while(!ss.length) ss = readln.chomp.split; string res = ss[0]; ss.popFront; return res; }
T scan(T)(){ return scan.to!T; } T[] scan(T)(int n){ return n.iota.map!(i => scan!T()).array; }
T lowerTo(T)(ref T x, T y){ if(x > y) x = y; return x; } T raiseTo(T)(ref T x, T y){ if(x < y) x = y; return x; }

// ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- //

const long mod = 998244353;
void solve(){
    int a = scan!int, b = scan!int, c = scan!int, d = scan!int;
    long[][] xf = new long[][](c + 1, d + 1);
    long[][] yf = new long[][](c + 1, d + 1);
    long[][] zf = new long[][](c + 1, d + 1);
    long[][] sf = new long[][](c + 1, d + 1);
    log("xf:", xf), log("yf:", yf), log("zf:", zf), log("sf:", sf);

    foreach(long i; 1 .. c + 1) foreach(long j; 1 .. d + 1){
        if(i < a) continue;
        if(j < b) continue;
        if(i == a && j == b){
            xf[i][j] = 0, yf[i][j] = 0, zf[i][j] = 0, sf[i][j] = 1;
        }
        else if(i == a && j == b + 1){
            xf[i][j] = a, yf[i][j] = 0, zf[i][j] = 0, sf[i][j] = a;
        }
        else if(i == a + 1 && j == b){
            xf[i][j] = 0, yf[i][j] = b, zf[i][j] = 0, sf[i][j] = b;
        }
        else{
            xf[i][j] = sf[i][j - 1] * i % mod;
            yf[i][j] = sf[i - 1][j] * j % mod;
            zf[i][j] = sf[i - 1][j - 1] * (i - 1) * (j - 1) % mod;
            sf[i][j] = (xf[i][j] + yf[i][j] + mod - zf[i][j]) % mod;
        }
    }
    log("xf:", xf), log("yf:", yf), log("zf:", zf), log("sf:", sf);
    sf[c][d].print;
}

/*
元々の部分は全部黒だったとする
x: 上端は2個以上黒があり、右端は1個だけ黒
y: 上端は1個だけ黒があり、右端は2個以上黒
z: 上端も右端も1個だけ黒
s: これらの合計
*/

// 素数位数有限体
// 負の数を与えても大丈夫（Finite(-1) などは Finite(mod - 1) の意味になる）
import std.conv;
struct Finite{
	long value; static long mod = 1_000_000_007;
	this(long v){ value = val(v); }
	static long val(long v){ return (v + mod  - (v / mod) * mod) % mod; }
	bool opCast(T: bool)(){ return value != 0; }
	bool opEquals(Finite b){ return(value == b.value); }
	string toString(){ return value.to!string; }

	Finite opUnary(string s){ long v;
		if(s == "+") v = value;
		else if(s == "-") v = mod - value;
		else if(s == "++") v = value + 1;
		else if(s == "--") v = value + mod - 1;
		else assert(0, "Operator unary " ~ s ~ " not implemented");
		return Finite(v);
	}

	Finite opBinary(string s)(Finite b){ return opBinary!s(b.value); }
	Finite opBinary(string s)(long u){ long v;
		if(s == "+") v = value + u;
		else if(s == "-") v = value + mod - u;
		else if(s == "*") v = value * u;
		else if(s == "/") v = value * inv(u);
		else assert(0, "Operator " ~ s ~ " not implemented");
		return Finite(v);
	}
	Finite opBinaryRight(string s)(long u){ long v;
		if(s == "+") v = u + value;
		else if(s == "-") v = u + mod - value;
		else if(s == "*") v = u * value;
		else if(s == "/") v = u * invvalue;
		else assert(0, "Operator " ~ s ~ " not implemented");
		return Finite(v);
	}
	Finite opAssign(long v){ value = v; return this; }

	Finite opOpAssign(string s)(Finite b){ return opOpAssign!s(b.value); }
	Finite opOpAssign(string s)(long v){
		if(s == "+") value = (value + v) % mod;
		else if(s == "-") value = (value + mod - v) % mod;
		else if(s == "*") value = (value * v) % mod;
		else if(s == "/") value = (value * inv(v)) % mod;
		else assert(0, "Operator " ~ s ~ "= not implemented");
		return this;
	}
	
	private static long[] _inv = [0, 1];
	long invvalue(){ return inv(value); }
	long inv(long v){ int i = val(v).to!int;
		while(i >= _inv.length){
			_inv ~= _inv[(mod % $).to!int] * (mod - mod / _inv.length) % mod;
		}
		return _inv[i];
	}
	
}