E.cpp

#include <bits/stdc++.h>
using namespace std;

using ll = long long;
const ll mod = 998244353;

// Time Complexity: O(n + m)
// Memory Complexity: O(n + m)

struct dsu {
	int c=0;
	vector<int> p, sz;

	dsu() {}
	dsu(int n):c(n),p(n),sz(n,1){ iota(p.begin(),p.end(),0); }

	int make_set(){
		int i=p.size();
		p.push_back(i); sz.push_back(1); c++;
		return i;
	}

	int find(int x){ return x==p[x]?x:p[x]=find(p[x]); }

	bool unite(int a,int b){
		a=find(a), b=find(b);
		if(a==b) return 0;
		if(sz[a]<sz[b]) swap(a,b);
		p[b]=a; sz[a]+=sz[b]; c--;
		return 1;
	}

	int size(int x){ return sz[find(x)]; }
	int count(){ return c; }
	int nodes(){ return p.size(); }
};

int main() {
	ios_base::sync_with_stdio(false); cin.tie(0);

	int n, m; cin >> n >> m;

	vector<ll> pow2(m+1); pow2[0] = 1;
	for(int i = 1; i <= m; i++) pow2[i] = (pow2[i-1]*2)%mod;

	vector<pair<int, int>> e(m);
	for(auto &[x, y] : e) {
		cin >> x >> y; x--; y--;
	}

	dsu DSU(n);
	ll ans = 0;
	for(int i = m-1; i >= 0; i--) {
		auto [x, y] = e[i];
		if(DSU.count() > 2) DSU.unite(x, y);
		else {
			if(DSU.find(x) == DSU.find(y)) continue;
			ans += pow2[i+1]; ans %= mod;
		}
	}
	cout << ans;

	return 0;
}