#include<bits/stdc++.h>
using namespace std;
#define pb push_back
const int lim=1e5+1;
int parent[lim];
int find(int i){
if(i==parent[i])return i;
return parent[i]=find(parent[i]);
}
void unite(int i,int j){
i=find(i),j=find(j);
parent[i]=j;
}
struct vec{
int*targ=new int[5],size=5,have=0;
void pb(int t){
if(have==size){
int*newy=new int[size*2];
for(int i=0;i<size;i++)newy[i]=targ[i];
size*=2;
delete targ;
targ=newy;
}
targ[have++]=t;
}
void clear(){
have=0;
delete targ;
}
};
vec v[lim];
vector<pair<int,int>>edges;
int tin[lim],tout[lim],tt=1;
int dfs(int node,int par){
if(tout[node])return tout[node];
tout[node]=tin[node]=tt++;
for(int i=0;i<v[node].have;i++){
int j=v[node].targ[i];
if(j==par)continue;
int res=dfs(j,node);
if(res<=tin[node]){
unite(node,j);
}
tout[node]=min(tout[node],res);
}
return tout[node];
}
int n,m;
void findans(){
for(auto[x,y]:edges){
v[find(x)].pb(find(y));
v[find(y)].pb(find(x));
}
for(int i=1;i<=n;i++){
tout[i]=tin[i]=0;
}
tt=1;
for(int i=1;i<=n;i++){
if(!tout[i])dfs(i,0);
}
vector<pair<int,int>>edges1;
for(auto[x,y]:edges){
if(find(x)!=find(y))edges1.pb({x,y});
}
edges=edges1;
}
int main(){
cin>>n>>m;
for(int i=1;i<=n;i++)parent[i]=i;
for(int i=0;i<m;i++){
int x,y;
cin>>x>>y;
if(find(x)!=find(y))edges.pb({x,y});
if(edges.size()==200000)findans();
}
findans();
for(auto[x,y]:edges)cout<<x<<' '<<y<<'\n';
}
