#include <bits/stdc++.h>
using namespace std;
int n, m, depth[100001] = {0}, ps[100001] = {0}, par[100001] = {0};
vector<int> adj[100001];
bool seen[100001];
void dfs(int i) {
seen[i] = true;
for (int j: adj[i]) {
if (j == par[i]) continue;
if (par[j] == i) par[j] = -1;
if (par[j] == -1) continue;
if (seen[j]) {
if (depth[j] > depth[i]) continue;
ps[i]++;
ps[j]--;
} else {
depth[j] = depth[i] + 1;
par[j] = i;
dfs(j);
ps[i] += ps[j];
}
}
}
int main() {
cin >> n >> m;
for (int i = 0; i < m; ++i) {
int a, b;
cin >> a >> b;
adj[a].emplace_back(b);
adj[b].emplace_back(a);
}
for (int i = 1; i <= n; ++i) {
if (not seen[i]) dfs(i);
}
for (int i = 1; i <= n; ++i) {
if (not ps[i] and par[i] > 0) cout << i << " " << par[i] << "\n";
}
}
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