#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
const int BLOCK = 10000;
const int MAXN = 100000;
vector <pair <int, tuple <int, int, int>>> graf[MAXN+5];
vector <pair <int, tuple <int, int, int>>> ngraf[MAXN+5];
bool visited[MAXN+5];
int in[MAXN+5];
int up[MAXN+5];
int gde[MAXN+5];
int ide[MAXN+5];
int tjm;
void dfs_bridges(int v, int gr){
visited[v] = 1;
in[v] = ++tjm;
up[v] = in[v];
for(auto c : graf[v]){
if(visited[c.first]){
if(get<2>(c.second) == gr) continue;
up[v] = min(up[v], up[c.first]);
}
else{
dfs_bridges(c.first, get<2>(c.second));
up[v] = min(up[v], up[c.first]);
}
}
}
void dfs_connect(int v, tuple <int, int, int> p, int lst){
int sd = lst;
visited[v] = 1;
ide[v] = v;
if(up[v] >= in[v]){
if(lst){
ngraf[v].push_back({lst, p});
ngraf[lst].push_back({v, p});
}
sd = v;
}
else ide[v] = gde[lst];
for(auto c : graf[v]){
if(!visited[c.first]) dfs_connect(c.first, c.second, sd);
}
}
int main(){
ios_base::sync_with_stdio(false), cin.tie(0);
cout.precision(10);
cout << fixed;
int n, m;
cin >> n >> m;
for(int i=1; i<=n; i++){
gde[i] = i;
}
int svih = 0;
while(m > 0){
for(int i=1; i<=min(m, BLOCK); i++){
int a, b;
cin >> a >> b;
++svih;
graf[gde[a]].push_back({gde[b], {a, b, svih}});
graf[gde[b]].push_back({gde[a], {b, a, svih}});
}
tjm = 0;
for(int i=1; i<=n; i++) visited[i] = 0;
for(int i=1; i<=n; i++) ngraf[i].clear();
for(int i=1; i<=n; i++){
if(!visited[gde[i]]) dfs_bridges(gde[i], 0);
}
for(int i=1; i<=n; i++) visited[i] = 0;
for(int i=1; i<=n; i++){
if(!visited[gde[i]]) dfs_connect(gde[i], {0, 0, 0}, 0);
}
for(int i=1; i<=n; i++){
gde[i] = ide[gde[i]];
graf[i].clear();
for(auto c : ngraf[i]) graf[i].push_back(c);
ngraf[i].clear();
}
m -= BLOCK;
}
vector <pair <int, int>> results;
for(int i=1; i<=n; i++){
for(auto c : graf[i]) results.push_back({get<0>(c.second), get<1>(c.second)});
}
sort(results.begin(), results.end());
for(int i=0; i<results.size(); i++) if(i == 0 || results[i] != results[i-1]) cout << results[i].first << " " << results[i].second << "\n";
return 0;
}
