#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <cmath>
#include <vector>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <queue>
#include <ctime>
#include <cassert>
#include <complex>
#include <string>
#include <cstring>
#include <chrono>
#include <random>
#include <queue>
#include <bitset>
#include <stack>
#include <functional>

#ifdef LOCAL
    #define eprintf(...) fprintf(stderr, __VA_ARGS__)
#else
    #define eprintf(...) 42
#endif

#define rep_(i, a_, b_, a, b, ...) for (int i = (a), i##_len = (b); i < i##_len; ++i)
#define rep(i, ...) rep_(i, __VA_ARGS__, __VA_ARGS__, 0, __VA_ARGS__)
#define reprev_(i, a_, b_, a, b, ...) for (int i = (b-1), i##_min = (a); i >= i##_min; --i)
#define reprev(i, ...) reprev_(i, __VA_ARGS__, __VA_ARGS__, 0, __VA_ARGS__)
#define all(x) (x).begin(), (x).end()
template <class T> bool chmax(T &a, const T &b) { if (a < b) { a = b; return 1; } return 0; }
template <class T> bool chmin(T &a, const T &b) { if (b < a) { a = b; return 1; } return 0; }
// template <class T> T gcd(T a, T b) { return b ? gcd(b, a % b) : a; }
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair <int,int> P;
typedef long double ld;

constexpr int MOD = 998244353;

// + - * / ^
int mod(int a)
{
    int res = a % MOD;
    if(res < 0) {
        return res + MOD;
    }
    return res;
}
int mul_mod(int a, int b)
{
    ll res = ((ll)a * (ll)b) % MOD;
    return mod((int)res);
}
int pow_mod(int a, int b)
{
    ll res = 1;
    while (b > 0) {
        if(b & 1) {
            res = res * (ll)a % (ll)MOD;
        }
        a = mul_mod(a, a);
        b >>= 1;
    }
    return (int)res;
}
int inv_mod(int a)
{
    return pow_mod(a, MOD - 2);
}
int div_mod(int a, int b)
{
    return mul_mod(a, inv_mod(b));
}

// ! C
constexpr int FAC_MAX = 3000001;
ll fac[FAC_MAX], finv[FAC_MAX], inv[FAC_MAX];
void com_init()
{
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < FAC_MAX; i++){
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}
ll com_mod(int a, int b){
    if (a < b) return 0;
    if (a < 0 || b < 0) return 0;
    return fac[a] * (finv[b] * finv[a - b] % MOD) % MOD;
}

int a, b, c, d;
vector<vector<ll>> ans;

ll rec (int h, int w) {
    // eprintf("(%d,%d)\n", h, w);
    if (h < a || w < b) return 0;
    else if (ans[h][w] != 0) return ans[h][w];
    if (h == a) return (ans[h][w] = a * rec(h, w - 1) % MOD);
    if (w == b) return (ans[h][w] = b * rec(h - 1, w) % MOD);
    // eprintf("(%d,%d): %d\n", h, w, h + w - 2);
    ll x = h * rec(h, w - 1) + w * (rec(h - 1, w)) - ((h - 1) * (w - 1) * rec(h - 1, w - 1) % MOD);
    return (ans[h][w] = x % MOD);
}

int main (void)
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    cin >> a >> b >> c >> d;
    ans.resize(c + 1);
    rep (i, c + 1) ans[i].resize(d + 1);
    ans[a][b] = 1;
    cout << rec(c, d) << "\n";
    // rep (i, c + 1) {
    //     rep (j, d + 1) eprintf("%2d ", ans[i][j]);
    //     eprintf("\n");
    // }
    return 0;
}

Measured memory_bytes: 73860