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

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef double ld;
//#define ll __int128
//#define int ll
//#define int ll
//#define char ll
#define double ld
typedef vector<char> vc;
typedef vector<vc> vvc;
typedef vector<vvc> vvvc;
typedef pair<int, int> pii;
typedef pair<pii, pii> piii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<pii> vpi;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<short> vs;
typedef vector<vs> vvs;
typedef vector<vvs> vvvs;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<ld> vld;
typedef vector<vld> vvld;
typedef vector<vvld> vvvld;
typedef vector<string> vst;
typedef vector<vst> vvst;
typedef pair<ld, ld> pld;

#define inmin(a, b) a = min(a, (b))
#define inmax(a, b) a = max(a, (b))
#define ALL(a) a.begin(),a.end()
#define RALL(a) a.rbegin(),a.rend()
#define sqr(x) ((x) * (x))
#define fori(i, n) for(int i = 0; i < int(n); ++i)
#define SZ(a) ((int)((a).size()))
#define triple(T) tuple<T, T, T>
#define quad(T) tuple<T, T, T, T>
#define watch(x) cerr << (#x) << " = " << (x) << endl;

#ifdef MAX_HOME
#define cerr cout
#else
#define cerr if (false) cerr
#endif

const double PI = 2 * acos(0.0);
//#define rand shittttty_shit
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng_64(chrono::steady_clock::now().time_since_epoch().count());

const string DIGITS = "0123456789";
const string ALPH = "abcdefghijklmnopqrstuvwxyz";


template<class T0, class T1>
inline ostream &operator<<(ostream &out, pair<T0, T1> &a) {
    return out << "{" << a.first << ", " << a.second << "}";
}

template<class T0, class T1>
inline istream &operator>>(istream &in, pair<T0, T1> &a) {
    return in >> a.first >> a.second;
}

template<class T0, class T1, class T2>
inline ostream &operator<<(ostream &out, tuple<T0, T1, T2> &a) {
    return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a) << "}";
}

template<class T0, class T1, class T2, class T3>
inline ostream &operator<<(ostream &out, tuple<T0, T1, T2, T3> &a) {
    return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a) << ", " << get<3>(a) << "}";
}

template<class T>
inline ostream &operator<<(ostream &out, vector<T> &a) {
    out << "[";
    fori (i, a.size())out << a[i] << vector<string>{", ", "]  "}[i + 1 == a.size()];
    return out;
}


void smain();


signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
#ifdef MAX_HOME
    freopen("input.txt", "r", stdin);
    clock_t start = clock();
#endif
    cout << setprecision(12) << fixed;
    smain();
#ifdef MAX_HOME
    cout << "\n\nTOTAL EXECUTION TIME: " << float(clock() - start) / CLOCKS_PER_SEC << endl;
#endif
    return 0;
}

const int M = 998244353;

int pw(int a, int n = M - 2) {
    int ret = 1;
    while (n) {
        if (n & 1)
            ret = (ll) ret * a % M;
        a = (ll) a * a % M;
        n >>= 1;
    }
    return ret;
}

const int N = 3030;

int dp[N][N];


int sum1[N][N];
int sum2[N][N];

int inv[N];

void insum(int &a, int b) {
    a = (a + b < M ? a + b : a + b - M);
}


void smain() {
    int a, b, c, d;
    cin >> a >> b >> c >> d;
    int n = c - a;
    int m = d - b;

    for (int i = 0; i < N; ++i) {
        inv[i] = pw(i);
    }

    for (int i = 0; i < N; ++i) {
        dp[i][0] = pw(b, i);
        sum2[i][0] = (ll)dp[i][0] * pw(pw(i + a - 1, 0)) % M;
    }
    for (int j = 0; j < N; ++j) {
        dp[0][j] = pw(a, j);
        sum1[0][j] = (ll)dp[0][j] * pw(pw(j + b - 1, 0)) % M;
    }

    dp[0][0] = 1;

    for (int i = 1; i <= n; ++i) {
        for (int j = 1; j <= m; ++j) {
            dp[i][j] = (ll)dp[i - 1][j - 1] * (i + a - 1) % M * (j + b - 1) % M;
            int cur = (ll) sum1[i - 1][j] * pw(j + b - 1, i - 1) % M;
            insum(dp[i][j], cur);

            cur = (ll) sum2[i][j - 1] * pw(i + a - 1, j - 1) % M;
            insum(dp[i][j], cur);

            sum1[i][j] = (ll) dp[i][j] * pw(inv[j + b - 1], i) % M;
            sum2[i][j] = (ll) dp[i][j] * pw(inv[i + a - 1], j) % M;


            if (i) {
                insum(sum1[i][j], sum1[i - 1][j]);
            }
            if (j) {
                insum(sum2[i][j], sum2[i][j - 1]);
            }
        }
    }
    cout << dp[n][m];


}

Measured memory_bytes: 110332