/* winners never quit and quitters never win.
      #swap                                 */
      
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp> 
using namespace std;
using namespace __gnu_pbds;
#pragma GCC optimize ("-O3")
using ll = long long;
using ld = long double;
const ll mod = 998244353;
const ll inf = 1000000000000000000;
const ll rk = 256;
const ld PI = 3.141592653589793;

typedef tree<
int,
null_type,
less<int>,
rb_tree_tag,
tree_order_statistics_node_update>
ordered_set;

template <typename T>
void make_unique(vector<T>& vec) {
  sort(all(vec));
  vec.erase(unique(all(vec)), vec.end());
}

#define pb push_back
#define mp make_pair
#define vc vector
#define fs first
#define sec second
#define pq priority_queue
#define lb lower_bound
#define ub upper_bound
#define pll pair<ll,ll> 
#define pls pair<ll,string>
#define psl pair<string,ll>
#define plc pair<ll,char>
#define pcl pair<char,ll>
#define pss pair<string,string>
#define all(x) (x).begin(), (x).end()
#define tol(s) transform(s.begin(),s.end(),s.begin(),::tolower);
#define tou(s) transform(s.begin(),s.end(),s.begin(),::toupper);
#define printclock cerr<<"Time : "<<1000*(ld)clock()/(ld)CLOCKS_PER_SEC<<"ms\n";

#define error(args...) { string _s = #args; replace(_s.begin(), _s.end(), ',', ' '); stringstream _ss(_s); istream_iterator<string> _it(_ss); err(_it, args); }

void err(istream_iterator<string> it) {}
template<typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
	cerr << *it << " = " << a << endl;
	err(++it, args...);
}

#define rep(i, begin, end) for (__typeof(end) i = (begin) - ((begin) > (end)); i != (end) - ((begin) > (end)); i += 1 - 2 * ((begin) > (end)))
#define T ll t=0;cin>>t;for(ll test=0;test<t;test++)

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

ll nxt() {
    ll TemporaryVariable;
    cin >> TemporaryVariable;
    return TemporaryVariable;
}

struct custom_hash {
    static uint64_t splitmix64(uint64_t x) {
        // http://xorshift.di.unimi.it/splitmix64.c
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }

    size_t operator()(uint64_t x) const {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};

ll fast_exp(ll base, ll exp1) {
    base%=mod;
    ll res=1;
    while(exp1>0) {
       if(exp1&1) res=(res*base)%mod;
       base=(base*base)%mod;
       exp1/=2;
    }
    return res%mod;
} 

ll add(ll x,ll y)
{
    return (x+y+mod)%mod;
}

ll mul(ll x,ll y)
{
    return (x*y)%mod;
}

 
int32_t main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
	//isprime();
	//coeff();
	/*freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);*/
    ll A=nxt(),B=nxt(),C=nxt(),D=nxt();
    ll n=C-A+1,m=D-B+1;
    ll dp[n][m];
    rep(a,0,n)
        rep(b,0,m)
            dp[a][b]=0;
    dp[0][0]=1;
    rep(a,1,n)
    {
        dp[a][0]=mul(dp[a-1][0],B);
    }
    rep(a,1,m)
    {
        dp[0][a]=mul(dp[0][a-1],A);
    }

    rep(a,1,n)
    {
        rep(b,1,m)
        {
            ll temp=mul(dp[a-1][b],B+b);
            temp=add(temp,mul(dp[a][b-1],A+a));
            temp=add(temp,-mul(dp[a-1][b-1],mul(A+a-1,B+b-1)));
            dp[a][b]=temp;
        }
    }
    cout<<dp[n-1][m-1]<<endl;
	printclock;
	return 0;
}

Measured memory_bytes: 74016