#include<stdio.h>
#include<math.h>
#include<algorithm>
#include<queue>
#include<deque>
#include<stack>
#include<string>
#include<string.h>
#include<vector>
#include<set>
#include<map>
#include<bitset>
#include<stdlib.h>
#include<cassert>
#include<time.h>
#include<bitset>
using namespace std;
const long long mod=998244353;
const long long inf=mod*mod;
const long long d2=(mod+1)/2;
const long double EPS=1e-9;
const long double PI=acos(-1.0);
int ABS(int a){return max(a,-a);}
long long ABS(long long a){return max(a,-a);}
long double ABS(long double a){return max(a,-a);}
long long fact[110000];
long long finv[110000];
long long inv[110000];
long long dp[3100][6100];
long long C(int a,int b){
if(b<0||a<b)return 0;
return fact[a]*finv[b]%mod*finv[a-b]%mod;
}
int main(){
fact[0]=finv[0]=inv[1]=1;
for(int i=2;i<110000;i++){
inv[i]=(mod-(mod/i)*inv[mod%i]%mod)%mod;
}
for(int i=1;i<110000;i++){
fact[i]=fact[i-1]*i%mod;
finv[i]=finv[i-1]*inv[i]%mod;
}
int a,b;scanf("%d%d",&a,&b);
dp[0][0]=1;
for(int i=0;i<a;i++){
for(int j=0;j<b;j++){
if(!dp[i][j])continue;
dp[i+1][j]=(dp[i+1][j]+dp[i][j])%mod;
dp[i+1][j+1]=(dp[i+1][j+1]+dp[i][j])%mod;
dp[i+1][j+2]=(dp[i+1][j+2]+dp[i][j])%mod;
}
}
long long ret=0;
for(int i=0;i<b;i++)ret=(ret+dp[a][i])%mod;
for(int i=1;i<=a;i++){
long long ks=C(a,i);
for(int j=1;j*2<=a;j++){
if(i+1>b||i*2-j*2+1<=b)continue;
// printf("%d %d: %lld\n",i,j,C(i-j*2,b-i-1));
ret=(ret+C(i-j*2,b-i-1)*ks)%mod;
}
if(i*2>b&&b%2==1){
ret=(ret+ks)%mod;
}
}
printf("%lld\n",ret);
}
./Main.cpp: In function ‘int main()’:
./Main.cpp:43:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
int a,b;scanf("%d%d",&a,&b);
^