#include<bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i,j,k) for(int i=(j);i<=(k);i++)
#define per(i,j,k) for(int i=(j);i>=(k);i--)
#define pb emplace_back
#define mp make_pair
#define fi first
#define se second 
typedef vector<int> vi;
typedef pair<int,int> pi;

const int N=4e5+5, mod=998244353, i2=(mod+1)/2;
int qpow(int x,int y=mod-2){
	int res=1;
	while(y){
		if(y%2) res=res*x%mod;
		x=x*x%mod;
		y/=2;
	}
	return res;
}

namespace ntt{
	const int LG=19, S=1<<LG;
	int P[S];
	void init(){
		rep(i,0,LG-1){
			int stp=qpow(3,(mod-1)>>(i+1));
			P[1<<i]=1;
			rep(j,(1<<i)+1,(2<<i)-1){
				P[j]=P[j-1]*stp%mod;
			}
		}
	}
	void DIF(vi &a){
		per(i,LG-1,0){
			int len=1<<i;
			for(int j=0;j<S;j+=len*2){
				int idx=len;
				rep(k,j,j+len-1){
					int A=a[k], B=a[k+len];
					a[k]=(A+B)%mod, a[k+len]=(A-B+mod)*P[idx++]%mod;
				}
			}
		}
	}
	void DIT(vi &a){
		rep(i,0,LG-1){
			int len=1<<i;
			for(int j=0;j<S;j+=len*2){
				int idx=len;
				rep(k,j,j+len-1){
					int A=a[k], B=a[k+len]*P[idx++]%mod;
					a[k]=(A+B)%mod, a[k+len]=(A-B+mod)%mod;
				}
			}
		}
		int iv=qpow(i2, LG);
		reverse(a.begin()+1,a.end());
		for(int &x:a){
			(x*= iv )%=mod;
		}
	}
	vi mul(vi a,vi b){
		a.resize(S);
		b.resize(S);
		DIF(a); DIF(b);
		rep(i,0,S-1){
			(a[i]*= b[i] )%=mod;
		}
		DIT(a);
		return a;
	}
}
using ntt::mul;

int fac[N], ifac[N];
void init(){
	fac[0]=1;
	rep(i,1,N-1){
		fac[i]=fac[i-1]*i%mod;
	}
	ifac[N-1]=qpow(fac[N-1]);
	per(i,N-1,1){
		ifac[i-1]=ifac[i]*i%mod;
	}
}
int C(int m,int n){
	return n<0 || n>m? 0: fac[m]*ifac[n]%mod*ifac[m-n]%mod;
}

signed main(){
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	#ifndef ONLINE_JUDGE
	assert(freopen(".in","r",stdin));
	assert(freopen(".out","w",stdout));
	#endif

	ntt::init();
	init();
	int n,m; cin>>n>>m;
	int ans=0;
	// rep(i,0,n-1){
	// 	rep(j,0,m-1){
	// 		(ans+= C(i+j,i)*C(i+j,i)-C(i+j,i-1)*C(i+j,j-1) )%=mod;
	// 	}
	// }
	vi x(n), y(m), z;
	rep(i,0,n-1){
		x[i]=ifac[i]*ifac[i]%mod;
	}
	rep(i,0,m-1){
		y[i]=ifac[i]*ifac[i]%mod;
	}
	z=mul(x,y);
	rep(i,0,n+m-1){
		(ans+= fac[i]*fac[i]%mod*z[i] )%=mod;
	}
	rep(i,0,n-1){
		x[i]=(i==0? 0: ifac[i-1]*ifac[i+1]%mod);
	}
	rep(i,0,m-1){
		y[i]=(i==0? 0: ifac[i-1]*ifac[i+1]%mod);
	}
	z=mul(x,y);
	rep(i,0,n+m-1){
		(ans-= fac[i]*fac[i]%mod*z[i] )%=mod;
	}

	(ans*= 2 )%=mod;
	rep(i,1,n-2){
		(ans+= ( C(m-2+i,i-1)*C(m-2+i,i-1)-C(m-2+i,i)*C(m-2+i,i-2) )%mod*(n-1-i) )%=mod;
	}
	rep(i,1,m-2){
		(ans+= ( C(n-2+i,i-1)*C(n-2+i,i-1)-C(n-2+i,i)*C(n-2+i,i-2) )%mod*(m-1-i) )%=mod;
	}
	ans+= 2;
	(ans-= C(n+m-2,n-1)*C(n+m-2,n-1)-C(n+m-2,n-2)*C(n+m-2,m-2) )%=mod;
	// (ans+= C())
	(ans+= mod )%=mod;
	cout<< ans <<'\n';
}