2019 ccpc秦皇岛

using namespace std;
const int inf = 0x3f3f3f3f;
const double eps = 1e-6;
const int N = 3e5+7;
typedef long long ll;
const ll mod = 998244353 ;
using namespace std;
vector<int> G[N];
int d[N],vis[N];
ll qpow(ll a,ll b){
    ll ans=1; ll base=a;
    while(b){
        if(b&1) ans=ans*base%mod;
        base=base*base%mod;
        b>>=1;
    }
    return ans;
}
ll res=1;
ll num=0;
void dfs(int u,int fa,int cnt){
    //cout<<u<<endl;
    d[u]=cnt;
    for(int i=0;i<G[u].size();i++){
        int v=G[u][i];
        if(v==fa) continue; 
        if(!vis[v]){
            vis[v]=1;
            dfs(v,u,cnt+1);
            vis[v]=2; 
        }else if(vis[v]==1){
            //cout<<cnt-d[v]+1<<endl;
            res=res*(qpow(2,cnt-d[v]+1)-1)%mod;
            num+=(cnt-d[v]+1);
        }else if(vis[v]==2){
        }
    }
}
int main(){
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    int n,m;
    while(cin>>n>>m){
        for(int i=1;i<=n;i++) G[i].clear();
        memset(vis,0,sizeof(vis));
        memset(d,0,sizeof(d));
        res=1;
        num=0;
        for(int i=1;i<=m;i++){
            int u,v; cin>>u>>v;
            G[u].push_back(v);
            G[v].push_back(u); 
        }
        vis[1]=1;
        dfs(1,0,1);
    //    for(int i=1;i<=n;i++)
    //        cout<<d[i]<<endl;
    //    cout<<res<<endl;
        //cout<<num<<endl;
        cout<<res*qpow(2,m-num)%mod<<endl;
    }
    return 0;
}