#include <bits/stdc++.h>
using namespace std;
const int nmax = 2e5 + 1, mod = 1e6 + 7;
struct DSU {
int root[nmax], sz[nmax];
void init(int n) {
for(int i = 1; i <= n; i++) {
root[i] = i;
sz[i] = 1;
}
}
int find(int a) {
if(root[a] == a) {
return a;
}
return root[a] = find(root[a]);
}
void unite(int a, int b) {
assert(a != b);
if(sz[a] > sz[b]) {
swap(a, b);
}
root[a] = b;
sz[b] += sz[a];
}
} d1, d2;
vector<int> adj[nmax], tj[nmax];
stack<int> st;
int low[nmax];
int t[nmax];
bool f[nmax];
int ind, comp;
void dfs(int i, int anc = 0) {
// cout << "!" << i << " " << anc << '\n';
f[i] = 1;
st.push(i);
t[i] = low[i] = t[anc] + 1;
for(auto it : adj[i]) {
//cout << "!" << i << " " << it << '\n';
if(f[it] && it != anc) {
low[i] = min(low[i], t[it]);
} else if(!f[it]) {
dfs(it, i);
low[i] = min(low[i], low[it]);
if(t[i] <= low[it]) {
if(st.top() == it) {
cout << i << " " << it << '\n';
}
while(st.top() != it) {
st.pop();
}
st.pop();
}
}
}
}
int32_t main(){
ios_base::sync_with_stdio(0);cin.tie(0);
int n, m;
cin >> n >> m;
d1.init(n), d2.init(n);
for(int i = 1; i <= m; i++) {
int a, b;
cin >> a >> b;
if(d1.find(a) != d1.find(b)) {
d1.unite(d1.find(a), d1.find(b));
adj[a].push_back(b);
adj[b].push_back(a);
} else if(d2.find(a) != d2.find(b)) {
d2.unite(d2.find(a), d2.find(b));
adj[a].push_back(b);
adj[b].push_back(a);
}
}
for(int i = 1; i <= n; i++) {
if(!f[i]) {
while(!st.empty()) {
st.pop();
}
dfs(i);
}
}
return 0;
}
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