#include <stdio.h>
 #include <bits/stdc++.h>






using namespace std;




template<class T, size_t... I>
void print_tuple(ostream& s, T const& a, index_sequence<I...>){
  using swallow = int[];
  (void)swallow{0, (void(s << (I == 0? "" : ", ") << get<I>(a)), 0)...};
}

template<class T>
ostream& print_collection(ostream& s, T const& a);
template<class... A>
ostream& operator<<(ostream& s, tuple<A...> const& a);
template<class A, class B>
ostream& operator<<(ostream& s, pair<A, B> const& a);

template<class T, size_t I>
ostream& operator<<(ostream& s, array<T, I> const& a) { return print_collection(s, a); }
template<class T>
ostream& operator<<(ostream& s, vector<T> const& a) { return print_collection(s, a); }
template<class T>
ostream& operator<<(ostream& s, deque<T> const& a) { return print_collection(s, a); }
template<class T, class U>
ostream& operator<<(ostream& s, multimap<T, U> const& a) { return print_collection(s, a); }
template<class T>
ostream& operator<<(ostream& s, multiset<T> const& a) { return print_collection(s, a); }
template<class T, class U>
ostream& operator<<(ostream& s, map<T, U> const& a) { return print_collection(s, a); }
template<class T>
ostream& operator<<(ostream& s, set<T> const& a) { return print_collection(s, a); }

template<class T>
ostream& print_collection(ostream& s, T const& a){
  s << '[';
  for(auto it = begin(a); it != end(a); ++it){
    s << *it;
    if(it != prev(end(a))) s << " ";
  }
  return s << ']';
}

template<class... A>
ostream& operator<<(ostream& s, tuple<A...> const& a){
  s << '(';
  print_tuple(s, a, index_sequence_for<A...>{});
  return s << ')';
}

template<class A, class B>
ostream& operator<<(ostream& s, pair<A, B> const& a){
  return s << "(" << get<0>(a) << ", " << get<1>(a) << ")";
}







using li = long long int;
using lu = long long unsigned;
using ld = long double;


using pii = tuple<li, li>;
using piii = tuple<li, li, li>;
using piiii = tuple<li, li, li, li>;
using vi = vector<li>;
using vii = vector<pii>;
using viii = vector<piii>;
using vvi = vector<vi>;
using vvii = vector<vii>;
using vviii = vector<viii>;

template<class T>
using min_queue = priority_queue<T, vector<T>, greater<T> >;
template<class T>
using max_queue = priority_queue<T>;

struct empty_t {};



namespace tuple_access {

  struct xx_t {} xx;
  struct yy_t {} yy;
  struct zz_t {} zz;
  struct ww_t {} ww;

  template<class T>
  typename tuple_element<0,T>::type& operator^(T& v, xx_t) { return get<0>(v); }
  template<class T>
  typename tuple_element<0,T>::type const& operator^(T const& v, xx_t) { return get<0>(v); }
  template<class T>
  typename tuple_element<0,T>::type&& operator^(T&& v, xx_t) { return get<0>(v); }

  template<class T>
  typename tuple_element<1,T>::type& operator^(T& v, yy_t) { return get<1>(v); }
  template<class T>
  typename tuple_element<1,T>::type const& operator^(T const& v, yy_t) { return get<1>(v); }
  template<class T>
  typename tuple_element<1,T>::type&& operator^(T&& v, yy_t) { return get<1>(v); }

  template<class T>
  typename tuple_element<2,T>::type& operator^(T& v, zz_t) { return get<2>(v); }
  template<class T>
  typename tuple_element<2,T>::type const& operator^(T const& v, zz_t) { return get<2>(v); }
  template<class T>
  typename tuple_element<2,T>::type&& operator^(T&& v, zz_t) { return get<2>(v); }

  template<class T>
  typename tuple_element<3,T>::type& operator^(T& v, ww_t) { return get<3>(v); }
  template<class T>
  typename tuple_element<3,T>::type const& operator^(T const& v, ww_t) { return get<3>(v); }
  template<class T>
  typename tuple_element<3,T>::type&& operator^(T&& v, ww_t) { return get<3>(v); }
}
using namespace tuple_access;


int ilog2(int x){ return 31 - __builtin_clz(x); }

template <class T>
struct identity : std::unary_function <T, T> {
  T operator() (const T& x) const {return x;}
};

template<class T>
T& smin(T& x, T const& y) { x = min(x,y); return x; }

template <class T>
T& smax(T& x, T const& y) { x = max(x, y); return x; }


template<typename T>
T isqrt(T const&x){
  static_assert(is_integral<T>::value, "is_integral<T>::value");
  assert(x>=T(0));
  T ret = static_cast<T>(sqrtl(x));
  while(ret>0 && ret*ret>x) --ret;
  while(x-ret*ret>2*ret) ++ret;
  return ret;
}

template<typename T>
T icbrt(T const&x) {
  static_assert(is_integral<T>::value, "is_integral<T>::value");
  assert(x>=T(0));
  T ret = static_cast<T>(cbrt(x));
  while(ret>0 && ret*ret*ret>x) --ret;
  while(x-ret*ret*ret>3*ret*(ret+1)) ++ret;
  return ret;
}



template<li M = 998'244'353>
struct Zn {
  static_assert(M > 2, "M > 2");
  static_assert(M < (1ll<<31), "M < (1ll<<31)");
  int value;

  Zn() : value(0) { }

  Zn(int x) : value(x%M) {
    if(value < 0) value += M;
  }

  Zn(li x) : value(x%M) {
    if(value < 0) value += M;
  }

  Zn& operator+=(Zn const& o) {
    value += o.value;
    if(value >= M) value -= M;
    return *this;
  }

  Zn& operator-=(Zn const& o) {
    value += M - o.value;
    if(value >= M) value -= M;
    return *this;
  }

  Zn& operator*=(Zn const& o) {
    value = ((li)value*(li)o.value)%M;
    return *this;
  }

  Zn& operator/=(Zn const& o) {
    return operator*=(o.inverse());
  }

  Zn operator-() const { Zn r; r.value = value ? M-value : 0; return r; }
  Zn operator+(Zn const& o) const { Zn r; r.value = value+o.value; if(r.value>=M) r.value -= M; return r; }
  Zn operator-(Zn const& o) const { Zn r; r.value = value+M-o.value; if(r.value>=M) r.value -= M; return r; }
  Zn operator*(Zn const& o) const { return Zn((li)value * (li)o.value); }
  Zn operator/(Zn const& o) const { Zn a = *this; a /= o; return a; }

  Zn inverse() const {
    int a = value, b = M, u = 0, v = 1;
    while (a != 0) {
      int t = b / a;
      b -= t * a; swap(a, b);
      u -= t * v; swap(u, v);
    }
    return Zn(u);
  }

  bool operator==(Zn const& o) const { return value == o.value; }
  bool operator!=(Zn const& o) const { return value != o.value; }
  bool operator<(Zn const& o) const { return value < o.value; }
  bool operator>(Zn const& o) const { return value > o.value; }
  bool operator<=(Zn const& o) const { return value <= o.value; }
  bool operator>=(Zn const& o) const { return value >= o.value; }
};

template<li M>
Zn<M> pow(Zn<M> a, li b) {
  Zn<M> r = 1;
  while(b){
    if(b&1) r = r*a;
    a = a * a;
    b /= 2;
  }
  return r;
}

template<li M>
Zn<M> operator+(int const& x, Zn<M> const& o) { return Zn<M>(x) + o; }
template<li M>
Zn<M> operator+(li const& x, Zn<M> const& o) { return Zn<M>(x) + o; }

template<li M>
Zn<M> operator*(int const& x, Zn<M> const& o) { return Zn<M>(x) * o; }
template<li M>
Zn<M> operator*(li const& x, Zn<M> const& o) { return Zn<M>(x) * o; }

template<li M>
Zn<M> operator/(int const& x, Zn<M> const& o) { return Zn<M>(x) / o; }
template<li M>
Zn<M> operator/(li const& x, Zn<M> const& o) { return Zn<M>(x) / o; }


template<li M>
ostream& operator<<(ostream& ss, Zn<M> const& a) {
  return ss << a.value;
}

template<li M>
istream& operator>>(istream& ss, Zn<M> &a) {
  li x; ss>>x;
  a = Zn<M>(x);
  return ss;
}
using ZN = Zn<998'244'353>;

const li N = 3333;

ZN dp[N][N];

int main(){
  ios::sync_with_stdio(0); cin.tie(0);
  li a,b,c,d; cin>>a>>b>>c>>d;
  dp[a][b] = 1;

  for(li i = (a+1); i <= (li)(c); ++i) { dp[i][b] = dp[i-1][b] * ZN(b); }
  for(li j = (b+1); j <= (li)(d); ++j) { dp[a][j] = dp[a][j-1] * ZN(a); }

  for(li i = (a+1); i <= (li)(c); ++i) {
    ZN acc = dp[i-1][b] * ZN(b);
    for(li j = (b+1); j <= (li)(d); ++j) {
      dp[i][j] += acc;
      dp[i][j] += dp[i-1][j] * ZN(j);
      acc *= ZN(i);
      acc += dp[i-1][j] * ZN(j);
    }
  }
  cout << dp[c][d] << endl;
  return 0;
}


Measured memory_bytes: 47044