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

// Created by White Knife on 15/04/20.
// doot diddly donger cuckerino Hahahahahah

#pragma GCC optimize("O3")
#pragma GCC target("sse4")
#pragma GCC target("popcnt")


#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;
using namespace __gnu_cxx;
using namespace std;

// @formatter:off
#define F               first
#define S               second
#define all(x)          (x).begin(), (x).end()
#define sz(x)           int((x).size())
#define sim             template<typename T
#define ris             return *this
#define dor             > debug & operator <<
#define eni(x)          sim > typename enable_if<sizeof dud<T>(0) x 1, debug&>::type operator<<(T i)
sim> struct rge { T b, e; };
sim> rge<T> rang(T i, T j) { return rge<T>{i, j}; }
sim> auto dud(T *x) -> decltype(cerr << *x, 0);
sim> char dud(...);
struct debug {
#ifdef LOCAL
  ~debug() { cerr << endl; }
  eni(!=) { cerr << boolalpha << i; ris; }
  eni(==) { ris << rang(all(i)); }
  sim, typename U dor(pair<U, T> d) { ris << "(" << d.first << ", " << d.second << ")"; }
  sim dor(rge<T> d) { *this << "["; for (auto it = d.b; it != d.e; ++it) *this << ", " + 2 * (it == d.b) << *it; ris << "]"; }
#else
  sim dor(const T&) { ris; }
#endif
};
#define pr(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "

using ll = long long;
using ull = unsigned long long;
using ld = long double;
//using li = __int128;
//using uli = unsigned __int128;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vb = vector<bool>;

using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vpii = vector<pii>;
using vpll = vector<pll>;
template <typename T> using ordered_set = tree<T, null_type, less<>, rb_tree_tag, tree_order_statistics_node_update>;

const ld PI = acos(-1);

template<typename T> inline T mini(T& x, T y) { return x = min(x, y); }
template<typename T> inline T maxi(T& x, T y) { return x = max(x, y); }
template<typename T> int sgn(T val) { return (T(0) < val) - (val < T(0));}
template<typename T> T rand(T x, T y) { return rand() % (y - x + 1) + x; }
mt19937 rnd(chrono::high_resolution_clock::now().time_since_epoch().count());
template <typename T> T gcd(T x, T y) { return (y == T(0)) ? x : gcd(y, x % y); }
// @formatter:on





const long long MOD7 = 1000000007;
const long long MOD9 = 1000000009;
const long long MODF = 998244353;

long long MOD = MOD7;

template <class T>
inline T add(T& x, T y) {
  x += y;
  if (x >= MOD) x -= MOD;
  return x;
}

template <class T>
inline T sub(T& x, T y) {
  x -= y;
  if (x < 0) x += MOD;
  return x;
}

template <typename T>
T mul(T x, T y) {
  x %= MOD, y %= MOD;
  return (x * (long long) y) % MOD;
}

template <typename T, typename U>
T power(T base, U exp, T mod) {
  T res = 1;
  while (exp > 0) {
    if (exp & 1) { res = mul(res, base); }
    base = mul(base, base);
    exp >>= 1;
  }
  return res % mod;
}

template <typename T>
T inverse(T a, T m) {
  T u = 0, v = 1;
  while (a != 0) {
    T t = m / a;
    m -= t * a; swap(a, m);
    u -= t * v; swap(u, v);
  }
  assert(m == 1);
  return u;
}

template <typename T>
T lcm(T a, T b) {
  return a / gcd(a, b) * b;
}

template <typename T>
T power(const T& a, long long b) {
  if (b == 0) {
    return 1;
  }
  if ((b & 1) == 0) {
    T res = power(a, b >> 1);
    return res * res;
  } else {
    return power(a, b - 1) * a;
  }
}

template <typename T>
T factorial(int n) {
  T result = 1;
  for (int i = 2; i <= n; i++) {
    result *= i;
  }
  return result;
}

template <typename T>
std::vector<T> factorials(int length) {
  std::vector<T> result(length);
  if (length > 0) {
    result[0] = 1;
  }
  for (int i = 1; i < length; i++) {
    result[i] = result[i - 1] * i;
  }
  return result;
}

template <typename T>
std::vector<T> powers(T base, int length) {
  std::vector<T> result(length);
  if (length > 0) {
    result[0] = 1;
  }
  for (int i = 1; i < length; i++) {
    result[i] = result[i - 1] * base;
  }
  return result;
}


template <typename T>
class Modular {
public:
  using Type = typename decay<decltype(T::value)>::type;
  
  constexpr Modular() : value() {}
  
  template <typename U>
  Modular(const U& x) {
    value = normalize(x);
  }
  
  template <typename U>
  static Type normalize(const U& x) {
    Type v;
    if (-mod() <= x && x < mod()) v = static_cast<Type>(x);
    else v = static_cast<Type>(x % mod());
    if (v < 0) v += mod();
    return v;
  }
  
  const Type& operator()() const { return value; }
  template <typename U>
  explicit operator U() const { return static_cast<U>(value); }
  constexpr static Type mod() { return T::value; }
  
  Modular& operator+=(const Modular& other) {
    if ((value += other.value) >= mod()) value -= mod();
    return *this;
  }
  Modular& operator-=(const Modular& other) {
    if ((value -= other.value) < 0) value += mod();
    return *this;
  }
  template <typename U> Modular& operator+=(const U& other) { return *this += Modular(other); }
  template <typename U> Modular& operator-=(const U& other) { return *this -= Modular(other); }
  Modular& operator++() { return *this += 1; }
  Modular& operator--() { return *this -= 1; }
  Modular operator++(int) {
    Modular result(*this);
    *this += 1;
    return result;
  }
  Modular operator--(int) {
    Modular result(*this);
    *this -= 1;
    return result;
  }
  Modular operator-() const { return Modular(-value); }
  
  template <typename U = T>
  typename enable_if<is_same<typename Modular<U>::Type, int>::value, Modular>::type& operator*=(const Modular& rhs) {
#ifdef _fWIN32
    uint64_t x = static_cast<int64_t>(value) * static_cast<int64_t>(rhs.value);
    uint32_t xh = static_cast<uint32_t>(x >> 32), xl = static_cast<uint32_t>(x), d, m;
    asm(
      "divl %4; \n\fun"
      : "=a" (d), "=d" (m)
      : "d" (xh), "a" (xl), "r" (MOD())
    );
    value = m;
#else
    value = normalize(static_cast<int64_t>(value) * static_cast<int64_t>(rhs.value));
#endif
    return *this;
  }
  template <typename U = T>
  typename enable_if<is_same<typename Modular<U>::Type, int64_t>::value, Modular>::type& operator*=(const Modular& rhs) {
    int64_t q = static_cast<int64_t>(static_cast<long double>(value) * rhs.value / mod());
    value = normalize(value * rhs.value - q * mod());
    return *this;
  }
  template <typename U = T>
  typename enable_if<!is_integral<typename Modular<U>::Type>::value, Modular>::type& operator*=(const Modular& rhs) {
    value = normalize(value * rhs.value);
    return *this;
  }
  
  Modular& operator/=(const Modular& other) { return *this *= Modular(inverse(other.value, mod())); }

//  template <typename U>
//  friend const Modular<U>& abs(const Modular<U>& v) { return v; }
  
  template <typename U>
  friend bool operator==(const Modular<U>& lhs, const Modular<U>& rhs);
  
  template <typename U>
  friend bool operator<(const Modular<U>& lhs, const Modular<U>& rhs);
  
  template <typename U>
  friend std::istream& operator>>(std::istream& stream, Modular<U>& number);

private:
  Type value;
};

template <typename T> bool operator==(const Modular<T>& lhs, const Modular<T>& rhs) { return lhs.value == rhs.value; }
template <typename T, typename U> bool operator==(const Modular<T>& lhs, U rhs) { return lhs == Modular<T>(rhs); }
template <typename T, typename U> bool operator==(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) == rhs; }

template <typename T> bool operator!=(const Modular<T>& lhs, const Modular<T>& rhs) { return !(lhs == rhs); }
template <typename T, typename U> bool operator!=(const Modular<T>& lhs, U rhs) { return !(lhs == rhs); }
template <typename T, typename U> bool operator!=(U lhs, const Modular<T>& rhs) { return !(lhs == rhs); }

template <typename T> bool operator<(const Modular<T>& lhs, const Modular<T>& rhs) { return lhs.value < rhs.value; }

template <typename T> Modular<T> operator+(const Modular<T>& lhs, const Modular<T>& rhs) {
  return Modular<T>(lhs) += rhs;
}
template <typename T, typename U> Modular<T> operator+(const Modular<T>& lhs, U rhs) { return Modular<T>(lhs) += rhs; }
template <typename T, typename U> Modular<T> operator+(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) += rhs; }

template <typename T> Modular<T> operator-(const Modular<T>& lhs, const Modular<T>& rhs) {
  return Modular<T>(lhs) -= rhs;
}
template <typename T, typename U> Modular<T> operator-(const Modular<T>& lhs, U rhs) { return Modular<T>(lhs) -= rhs; }
template <typename T, typename U> Modular<T> operator-(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) -= rhs; }

template <typename T> Modular<T> operator*(const Modular<T>& lhs, const Modular<T>& rhs) {
  return Modular<T>(lhs) *= rhs;
}
template <typename T, typename U> Modular<T> operator*(const Modular<T>& lhs, U rhs) { return Modular<T>(lhs) *= rhs; }
template <typename T, typename U> Modular<T> operator*(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) *= rhs; }

template <typename T> Modular<T> operator/(const Modular<T>& lhs, const Modular<T>& rhs) {
  return Modular<T>(lhs) /= rhs;
}
template <typename T, typename U> Modular<T> operator/(const Modular<T>& lhs, U rhs) { return Modular<T>(lhs) /= rhs; }
template <typename T, typename U> Modular<T> operator/(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) /= rhs; }

template <typename T, typename U>
Modular<T> power(const Modular<T>& a, const U& b) {
  assert(b >= 0);
  Modular<T> x = a, res = 1;
  U p = b;
  while (p > 0) {
    if (p & 1) res *= x;
    x *= x;
    p >>= 1;
  }
  return res;
}

template <typename T>
bool IsZero(const Modular<T>& number) {
  return number() == 0;
}

template <typename T>
string to_string(const Modular<T>& number) {
  return to_string(number());
}

template <typename T>
std::ostream& operator<<(std::ostream& stream, const Modular<T>& number) {
  return stream << number();
}

template <typename T>
std::istream& operator>>(std::istream& stream, Modular<T>& number) {
  typename common_type<typename Modular<T>::Type, int64_t>::type x;
  stream >> x;
  number.value = Modular<T>::normalize(x);
  return stream;
}

//constexpr int md = (int) 1e9 + 7;
//constexpr int md2 = md - 1;
constexpr int md = 998244353;
using Mint = Modular<std::integral_constant<decay<decltype(md)>::type, md>>;
//using Mint2 = Modular<std::integral_constant<decay<decltype(md2)>::type, md2>>;

/*
using ModType = int;
struct VarMod { static ModType value; };
ModType VarMod::value;
ModType& md = VarMod::value;
using Mint = Modular<VarMod>;
*/

const int MAXN = 3000 + 5;
int a, b, c, d;

vector<vector<Mint>> dp;

class BExtension {
public:
  
  void solve(std::istream& cin, std::ostream& cout) {
    cin >> a >> b >> c >> d;
    dp.clear();
    dp.resize(c + 1, vector<Mint>(d + 1, 0));
    dp[a][b] = 1;
    for (int i = 1; i <= c; ++i) {
      for (int j = 1; j <= d; ++j) {
        dp[i][j] += j * dp[i - 1][j];
        dp[i][j] += i * dp[i][j - 1];
        dp[i][j] -= (i - 1) * (j - 1) * dp[i - 1][j - 1];
      }
    }
    Mint ans = dp[c][d];
    cout << ans << '\n';
  }
};

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


Measured memory_bytes: 38560