#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for(int i=0;i<(n);i++)
#define Inf 1000000001

mint dp[4005][4005];
int main(){
	
	long long x,y;
	cin>>x>>y;
	if(x>4004||y>4004)return 0;
	//if(x>y)swap(x,y);
	
	dp[0][0] = 1;
	
	rep(i,4005){
		rep(j,4005){
			if(i!=4004)dp[i+1][j] += dp[i][j];
			if(j!=4004)dp[i][j+1] += dp[i][j];
			if(i!=4004&&j!=4004)dp[i+1][j+1] += dp[i][j]*2;
		}
	}
	
	mint ans = 0;
	
	rep(i,4005){
		rep(j,4005){
			if(i>x||j>y)continue;
			if(j-i != y-x)continue;
			ans += dp[i][j];
			//cout<<i<<','<<j<<','<<dp[i][j].val()<<endl;
		}
	}
	cout<<ans.val()<<endl;
			
	
	return 0;
}