#include <bits/stdc++.h>
using namespace std;
int n, m, a, b;
vector<pair<pair<int, int>, int>> edge;
vector<pair<pair<int, int>, int>> newedge;
int par[100005];
bool vis[100005], yas[200005];
int id[100005], c_id = 1, low[100005];
vector<pair<int, int>> adj[100005];
stack<int> stk;
int fpar(int x) {
return (x == par[x] ? x : (par[x] = fpar(par[x])));
}
void dfs(int x, int paredge) {
id[x] = low[x] = c_id++;
int c_mx = -1;
stk.push(x);
//cout << x;
for(auto &e:adj[x]) {
if(e.second == paredge) continue;
if(id[e.first]) low[x] = min(low[x], id[e.first]);
else {
dfs(e.first, e.second);
low[x] = min(low[x], low[e.first]);
c_mx = max(c_mx, low[e.first]);
}
}
if(id[x] == low[x]) {
if(paredge != 999999999) {
//cout << "yes " << x << " and edge no. " << paredge << '\n';
yas[paredge] = 1;
}
while(stk.top() != x) {
int e = stk.top(); stk.pop();
par[fpar(e)] = fpar(x);
}
stk.pop();
}
//if(c_mx >= id[x] && paredge != 999999999) yas[paredge] = 1;
}
void cleanedge() {
memset(vis, 0, sizeof vis); memset(yas, 0, sizeof yas); memset(id, 0, sizeof id);
for(auto e:edge) {
e.first.first = fpar(e.first.first); e.first.second = fpar(e.first.second);
adj[e.first.first].emplace_back(e.first.second, e.second);
adj[e.first.second].emplace_back(e.first.first, e.second);
}
for(int i=1;i<=n;i++) {
if(vis[fpar(i)]) continue;
dfs(fpar(i), 999999999);
}
newedge.clear(); int bruh = 0;
for(auto &e:edge) {
if(yas[e.second]) {
newedge.emplace_back(e.first, bruh++);
}
}
edge = newedge;
for(int i=1;i<=n;i++) adj[i].clear();
}
int main() {
cin.tie(0) -> sync_with_stdio(0);
cin >> n >> m;
for(int i=1;i<=n;i++) par[i] = i;
while(m--) {
cin >> a >> b;
edge.emplace_back(pair<int, int>(a, b), edge.size());
if(edge.size() == 200000) {
//do cleaning
cleanedge();
assert(edge.size() <= 100000); //hmmm??!?!?
}
}
cleanedge();
//cout << '\n';
for(auto &e:edge) cout << e.first.first << ' ' << e.first.second << '\n';
}
