// Problem: # 9479. And DNA
// Author: XZC(L_Wave)
// Language: Cpp/G++20
// Contest: 
// URL: https://qoj.ac/problem/9479
// Memory Limit: 1024 MB
// Time Limit: 1000 ms
// Create Time: not 2024-11-20 09:10:32, but 1926-08-17 11:45:14
// 
// Powered by CP Editor (https://cpeditor.org)

#include <bits/stdc++.h>
#define rep(i, a, b) for (int i = (a), i##ABRACADABRA = (b); i <= i##ABRACADABRA; i++)
#define drep(i, a, b) for (int i = (a), i##ABRACADABRA = (b); i >= i##ABRACADABRA; i--)
using namespace std;
using ll = long long;
constexpr ll mod=998244353;
constexpr int N=3;
struct mat{
  ll a[N][N];
  mat(int _ty=0){_ty?idm():clr();}
  void clr(){memset(a,0,sizeof(a));}
  void idm(){clr();rep(i,0,N-1)a[i][i]=1;}
  void dbg()const{
    cout<<"-----------------------\n";
    rep(i,0,N-1)rep(j,0,N-1)cout<<a[i][j]<<" \n"[j==N-1];
    cout<<"-----------------------\n";
  }
  ll&g(int x,int y){return a[x][y];}
  ll g(int x,int y)const{return a[x][y];}
  friend mat operator*(mat x,mat y){
    mat z;
    rep(i,0,N-1)rep(k,0,N-1)rep(j,0,N-1)
      (z.a[i][j]+=1ll*x.a[i][k]*y.a[k][j]%mod)%=mod;
    return z;
  }
  friend mat operator^(mat x,ll y){
    mat z;
    z.idm();
    // 在矩阵无法得到合适的单位矩阵（如特定 (min,+) 矩阵等）时
    // 可以 --y,z=x，然后像正常一样做（y=0 不适用）
    for (;y;y>>=1){
      if (y&1)z=z*x;
      x=x*x;
    }
    return z;
  }
}A;

int n,m;
map<int,ll>res;

ll solve(int m){
  // cout<<m<<endl;
  if (res.count(m))return res[m];
  return res[m]=(m&1?res[1]*solve(m>>1):solve(m>>1)+solve((m>>1)-1))%mod;
}

int main() {
  scanf("%d%d",&n,&m);
  A.g(0,1)=1;
  A.g(0,2)=1;
  A.g(1,0)=1;
  A.g(2,1)=1;
  A=A^n;
  res[0]=1;
  res[1]=(A.g(0,0)+A.g(1,1)+A.g(2,2))%mod;
  printf("%lld\n",solve(m));
  return 0;
}