//
// main.cpp
// C
//
// Created by Sajad Zare on 4/23/22.
//
#include <iostream>
#include <math.h>
#include <string>
#include <string.h>
#include <vector>
#include <cstring>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <deque>
#include <utility>
#include <cmath>
#include <algorithm>
#include <tuple>
#include <numeric>
#include <iomanip>
#include <bitset>
using namespace std;
const int maxn=1e5+2;
int parent[maxn];
int parent2[maxn];
//int sz[maxn];
//int sz2[maxn];
bitset<maxn>seen;
int st[maxn];
//int parent3[maxnn];
int lowest[maxn];
int tmm=0;
vector<int> N[maxn];
//vector<pair<int, int>>t1;
//vector<pair<int, int>>t2;
//map<pair<int, int>, int>sss;
int x,y;
int get_root(int v){
if (parent[v]!=v){
parent[v]=get_root(parent[v]);
}
return parent[v];
}
int get_root2(int v){
if (parent2[v]!=v){
parent2[v]=get_root2(parent2[v]);
}
return parent2[v];
}
bool Union(int u,int v){
u=get_root(u);
v=get_root(v);
if (u==v){
return 1;
}
parent[u]=v;
return 0;
}
bool Union2(int u,int v){
x=u;
y=v;
u=get_root2(u);
v=get_root2(v);
if (u==v){
return 0;
}
N[x].push_back(y);
N[y].push_back(x);
parent2[u]=v;
return 1;
}
void dfs(int node,int pp){
seen[node]=1;
tmm+=1;
st[node]=tmm;
lowest[node]=tmm;
//stft.push_back(node);
for (int n: N[node]){
if (seen[n]!=1){
//parent3[n]=node;
dfs(n,node);
lowest[node]=min(lowest[node], lowest[n]);
if (lowest[n]>st[node] && count(N[node].begin(),N[node].end(),n)==1){
cout << node << ' ' << n << "\n";
}
}
else if (n!=pp){
lowest[node]=min(lowest[node],st[n]);
}
}
//ft[node]=t;
//stft.push_back(node);
}
//const int M = 1000000007;
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int n,m;
cin >> n >> m;
for (int i=1;i<n+1;i++){
parent[i]=i;
//sz[i]=1;
}
for (int i=1;i<n+1;i++){
parent2[i]=i;
//sz2[i]=1;
}
int u,v;
for (int i=0;i<m;i++){
cin >> u >> v;
if (Union(u, v)){
Union2(u, v);
}
else{
N[u].push_back(v);
N[v].push_back(u);
}
}
for (int i=1;i<n+1;i++){
if (seen[i]!=1){
dfs(i,-1);
}
}
return 0;
}
