#include <bits/stdc++.h>
 
//    #include <boost/multiprecision/cpp_int.hpp>
// #define int long long
 #define inf  1000000007
 #define pa pair<int,int>
 #define ll long long
 #define pal pair<double,double>
 #define ppap pair<pa,int>
  #define PI 3.14159265358979323846
  #define paa pair<int,char>
  #define  mp make_pair
  #define  pb push_back
  #define EPS (1e-8)
                                          
    int dx[8]={0,1,0,-1,1,1,-1,-1};
    int dy[8]={1,0,-1,0,-1,1,1,-1};
                                            using namespace std;
                                   			class pa3{
                                            	public:
                                            	int x;
                                   				int y,z;
                                            	pa3(int x=0,int y=0,int z=0):x(x),y(y),z(z) {}
                                            	bool operator < (const pa3 &p) const{
                                            		if(x!=p.x) return x<p.x;
                                            		if(y!=p.y) return y<p.y;
                                            		 return z<p.z;
                                            		//return x != p.x ? x<p.x: y<p.y;
                                            	}
                                   				bool operator > (const pa3 &p) const{
                                            		if(x!=p.x) return x>p.x;
                                            		if(y!=p.y) return y>p.y;
                                            		 return z>p.z;
                                            		//return x != p.x ? x<p.x: y<p.y;
                                            	}
                                            	bool operator == (const pa3 &p) const{
                                            		return x==p.x && y==p.y && z==p.z;
                                            	}
                                            		bool operator != (const pa3 &p) const{
                                            			return !( x==p.x && y==p.y && z==p.z);
                                            	}
                                            
                                            };
                                            
                                            class pa4{
                                            	public:
                                            	int x;
                                            	int y,z,w;
                                            	pa4(int x=0,int y=0,int z=0,int w=0):x(x),y(y),z(z),w(w) {}
                                            	bool operator < (const pa4 &p) const{
                                            		if(x!=p.x) return x<p.x;
                                            		if(y!=p.y) return y<p.y;
                                            		if(z!=p.z)return z<p.z;
                                            		return w<p.w;
                                            		//return x != p.x ? x<p.x: y<p.y;
                                            	}
                                            	bool operator > (const pa4 &p) const{
                                            		if(x!=p.x) return x>p.x;
                                            		if(y!=p.y) return y>p.y;
                                            		if(z!=p.z)return z>p.z;
                                            		return w>p.w;
                                            		//return x != p.x ? x<p.x: y<p.y;
                                            	}
                                            	bool operator == (const pa4 &p) const{
                                            		return x==p.x && y==p.y && z==p.z &&w==p.w;
                                            	}
                                            		
                                            
                                            };
                                            class pa2{
                                            	public:
                                            	int x,y;
                                            	pa2(int x=0,int y=0):x(x),y(y) {}
                                            	pa2 operator + (pa2 p) {return pa2(x+p.x,y+p.y);}
                                            	pa2 operator - (pa2 p) {return pa2(x-p.x,y-p.y);}
                                            	bool operator < (const pa2 &p) const{
                                            		return y != p.y ? y<p.y: x<p.x;
                                            	}
                                            	bool operator > (const pa2 &p) const{
                                            		return x != p.x ? x<p.x: y<p.y;
                                            	}
                                            	bool operator == (const pa2 &p) const{
                                            		return abs(x-p.x)==0 && abs(y-p.y)==0;
                                            	}
                                            	bool operator != (const pa2 &p) const{
                                            		return !(abs(x-p.x)==0 && abs(y-p.y)==0);
                                            	}
                                            		
                                            
                                            };
                                            
 
                      
                                string itos( int i ) {
                                ostringstream s ;
                                s << i ;
                                return s.str() ;
                                }
                                 
                                int gcd(int v,int b){
                                	if(v==0) return b;
                                	if(b==0) return v;
                                	if(v>b) return gcd(b,v);
                                	if(v==b) return b;
                                	if(b%v==0) return v;
                                	return gcd(v,b%v);
                                }
                 
                            
                                int mod;
int extgcd(int a, int b, int &x, int &y) {
    if (b == 0) {
        x = 1;
        y = 0;
        return a;
    }
    int d = extgcd(b, a%b, y, x);
    y -= a/b * x;
    return d;
}
pa operator+(const pa & l,const pa & r) {   
    return {l.first+r.first,l.second+r.second};                                    
}    
pa operator-(const pa & l,const pa & r) {   
    return {l.first-r.first,l.second-r.second};                                    
}  
                                
                int pr[10000100];
                int inv[10000010];
                
                int beki(int wa,int rr,int warukazu){
                	if(rr==0) return 1%warukazu;
                	if(rr==1) return wa%warukazu;
                	wa%=warukazu;
                	if(rr%2==1) return ((ll)beki(wa,rr-1,warukazu)*(ll)wa)%warukazu;
                	ll zx=beki(wa,rr/2,warukazu);
                	return (zx*zx)%warukazu;
                }
 
                
    			int comb(int nn,int rr){
    				if(rr<0 || rr>nn || nn<0) return 0;
    				int r=pr[nn]*inv[rr];
    				r%=mod;
    				r*=inv[nn-rr];
    				r%=mod;
    				return r;
    			}
               
                void gya(int ert){
                	pr[0]=1;
                	for(int i=1;i<=ert;i++){
                		pr[i]=((ll)pr[i-1]*i)%mod;
                	}
                		inv[ert]=beki(pr[ert],mod-2,mod);
                	for(int i=ert-1;i>=0;i--){
                		inv[i]=(ll)inv[i+1]*(i+1)%mod;
                	}
                }
                
              //   cin.tie(0);
    		//	ios::sync_with_stdio(false);
    			//priority_queue<pa3,vector<pa3>,greater<pa3>> pq;            
                 //sort(ve.begin(),ve.end(),greater<int>());
 //   mt19937(clock_per_sec);
  //  mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count()) ;


// shoki(N)で初期化

// add_edge(x,y) でx<->yに枝追加 x!=y 多重辺OK
// [0,N)でグラフは連結

// shori()で実行

// same(x,y)で二つが同じ強連結成分に入ってるか
// id(x)で頂点xの連結成分番号


struct hasi{
private:
	int cnt=0;
	public:
int V;
	vector<vector<int>> gr,Cgr;
	vector<pa> eda;
	vector<int> eda_shu,imo,oya_eda,bridge,id;
	vector<bool> vis;
	int component_size;
	void shoki(int N){
		V=N;
		imo.resize(N,0);
		gr.resize(N,{});
		vis.resize(N,false);
		id.resize(N);
		oya_eda.resize(N);
	}
	
	void add_edge(int x,int y){
		eda.pb(mp(x,y));
		eda_shu.pb(0);
		gr[x].pb(cnt);
		gr[y].pb(cnt);
		cnt++;
	}
	
	
	
	void dfs(int r){
		vis[r]=1;
		for(auto v:gr[r]){
			if(eda_shu[v]!=0)continue;
			int to=r^eda[v].first^eda[v].second;
			if(vis[to]){
				eda_shu[v]=2;
				imo[r]++;
				imo[to]--;
			}
			else{
				eda_shu[v]=1;
				if(eda[v].first!=r)swap(eda[v].first,eda[v].second);
				oya_eda[to]=v;
				dfs(to);
			}
		}
	}
	
	int imo_dfs(int r){
		for(auto v:gr[r])if(eda_shu[v]==1 && eda[v].first==r)imo[r]+=imo_dfs(eda[v].second);
		if(r!=0 && imo[r]==0){
			bridge.pb(oya_eda[r]);
		}
		return imo[r];
	}
	
	void dfs_group(int r){
		for(auto v:gr[r])if(eda_shu[v]==1 && eda[v].first==r){
			if(imo[eda[v].second]==0){
				cnt++;
				id[eda[v].second]=cnt;
				Cgr[cnt].pb(id[r]);
				Cgr[id[r]].pb(cnt);
			}
			else id[eda[v].second]=id[r];
			dfs_group(eda[v].second);
		}
	}
	

	
	void shori(){
		dfs(0);
		imo_dfs(0);
		
		
		vector<pa>R;
		for(auto v:bridge)R.pb(mp(min(eda[v].first,eda[v].second),max(eda[v].first,eda[v].second)));
		sort(R.begin(),R.end());
		for(auto v:R)cout<<v.first<<" "<<v.second<<endl;
		
		component_size=bridge.size()+1;
		cnt=0;
		id[0]=0;
		Cgr.resize(component_size,{});
		dfs_group(0);
		
	}

	
	

};

signed main(){
	
	
cin.tie(0);
ios::sync_with_stdio(false);

	
int n,m;
	cin>>n>>m;
	hasi ss;
	ss.shoki(n);
	for(int i=0;i<m;i++){
		int a,b;
		cin>>a>>b;
		ss.add_edge(a,b);
	}
	ss.shori();
	return 0; 
 }


Measured memory_bytes: 4800