#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
struct bridge{
	vector<int>ord,low;
	vector<bool>art;
	vector<pair<int,int> >bridges;
	vector<vector<int> >G;
	bridge(int n_=0):ord(n_,-1),low(n_),art(n_,false),G(n_){}
	void add_edge(int u,int v)
	{
		G[u].push_back(v);
		G[v].push_back(u);
	}
	bool operator[](int a){return art[a];}
	bool is_bridge(int a,int b)
	{
		if(ord[a]>ord[b])swap(a,b);
		return ord[a]<low[b];
	}
	void dfs(int u,int p,int&cnt)
	{
		low[u]=ord[u]=cnt++;
		for(int&v:G[u])
		{
			if(ord[v]==-1)
			{
				dfs(v,u,cnt);
				low[u]=min(low[u],low[v]);
				art[u]=art[u]|ord[u]<=low[v];
				if(ord[u]<low[v])bridges.push_back(u<v?make_pair(u,v):make_pair(v,u));
			}
			else if(v!=p)
			{
				low[u]=min(low[u],ord[v]);
			}
		}
	}
	void build()
	{
		int k=1,cnt=0;
		low[0]=ord[0]=0;
		for(int&v:G[0])if(ord[v]==-1)
		{
			dfs(v,0,k);
			if(ord[0]<low[v])bridges.push_back(make_pair(0,v));
			cnt++;
		}
		if(cnt>=2)art[0]=true;
	}
};

int main()
{
	int n,m;cin>>n>>m;
	bridge P(n);
	vector<pair<int,int> >e;
	for(int i=0;i<m;i++)
	{
		int a,b;cin>>a>>b;
		P.add_edge(a,b);
		e.push_back(a<b?make_pair(a,b):make_pair(b,a));
	}
	P.build();
	sort(e.begin(),e.end());
	for(int i=0;i<e.size();i++)if(P.is_bridge(e[i].first,e[i].second))cout<<e[i].first<<" "<<e[i].second<<endl;
}

