import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


struct ModInt(int M_) {
  import std.conv : to;
  alias M = M_;
  int x;
  this(ModInt a) { x = a.x; }
  this(long a) { x = cast(int)(a % M); if (x < 0) x += M; }
  ref ModInt opAssign(long a) { return (this = ModInt(a)); }
  ref ModInt opOpAssign(string op)(ModInt a) {
    static if (op == "+") { x += a.x; if (x >= M) x -= M; }
    else static if (op == "-") { x -= a.x; if (x < 0) x += M; }
    else static if (op == "*") { x = cast(int)((cast(long)(x) * a.x) % M); }
    else static if (op == "/") { this *= a.inv(); }
    else static assert(false);
    return this;
  }
  ref ModInt opOpAssign(string op)(long a) {
    static if (op == "^^") {
      if (a < 0) return (this = inv()^^(-a));
      ModInt t2 = this, te = ModInt(1);
      for (long e = a; e > 0; e >>= 1) {
        if (e & 1) te *= t2;
        t2 *= t2;
      }
      x = cast(int)(te.x);
      return this;
    } else return mixin("this " ~ op ~ "= ModInt(a)");
  }
  ModInt inv() const {
    int a = x, b = M, y = 1, z = 0, t;
    for (; ; ) {
      t = a / b; a -= t * b;
      if (a == 0) {
        assert(b == 1 || b == -1);
        return ModInt(b * z);
      }
      y -= t * z;
      t = b / a; b -= t * a;
      if (b == 0) {
        assert(a == 1 || a == -1);
        return ModInt(a * y);
      }
      z -= t * y;
    }
  }
  ModInt opUnary(string op: "-")() const { return ModInt(-x); }
  ModInt opBinary(string op, T)(T a) const {
    return mixin("ModInt(this) " ~ op ~ "= a");
  }
  ModInt opBinaryRight(string op)(long a) const {
    return mixin("ModInt(a) " ~ op ~ "= this");
  }
  bool opCast(T: bool)() const { return (x != 0); }
  string toString() const { return x.to!string; }
}

enum MO = 998244353;
alias Mint = ModInt!MO;

enum LIM = 6005;

void main() {
  auto two = new Mint[LIM];
  two[0] = 1;
  foreach (i; 1 .. LIM) {
    two[i] = two[i - 1] * 2;
  }
  
  try {
    for (; ; ) {
      const A = readInt();
      const B = readInt();
      const C = readInt();
      const D = readInt();
      
      /*
      debug {
        if (C <= 5 && D <= 5) {
          auto board = new char[][](C, D);
          foreach (x; 0 .. C) {
            board[x][] = '.';
          }
          void dfs(int c, int d) {
            if (c == C && d == D) {
              foreach (x; 0 .. C) {
                writeln(board[x]);
              }
              writeln("--------");
              return;
            }
            if (c + 1 <= C) {
              foreach (y; 0 .. d) {
                board[c][y] = '#';
                dfs(c + 1, d);
                board[c][y] = '.';
              }
            }
            if (d + 1 <= D) {
              foreach (x; 0 .. c) {
                board[x][d] = '#';
                dfs(c, d + 1);
                board[x][d] = '.';
              }
            }
          }
          dfs(A, B);
        }
      }
      //*/
      
      auto dp = new Mint[][](C + 1, D + 1);
      dp[A][B] = 1;
      foreach (c; A + 1 .. C + 1) {
        dp[c][B] = Mint(B)^^(c - A);
      }
      foreach (d; B + 1 .. D + 1) {
        dp[A][d] = Mint(A)^^(d - B);
      }
      foreach (c; A + 1 .. C + 1) foreach (d; B + 1 .. D + 1) {
        dp[c][d] += dp[c - 1][d];
        dp[c][d] += dp[c][d - 1];
        dp[c][d] += Mint(d - 1) * dp[c - 1][d];
        dp[c][d] += Mint(c - 1) * dp[c][d - 1];
        dp[c][d] -= Mint(c - 1) * Mint(d - 1) * dp[c - 1][d - 1];
      }
      debug {
        if (C <= 10 && D <= 10) {
          foreach (c; 0 .. C + 1) {
            writeln(c, ": ", dp[c]);
          }
        }
      }
      
      writeln(dp[C][D]);
    }
  } catch (EOFException e) {
  }
}
