#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 1e5 + 7;
int n, m;
vector<int> g[N];
int low[N], tin[N];
bool vis[N];
int tt;
struct Dsu {
int t[N];
int root(int x) {
if (t[x] == x) return x;
return t[x] = root(t[x]);
}
void merge(int a, int b) {
a = root(a);
b = root(b);
if (a != b) t[b] = a;
}
bool same(int u, int v) {
return root(u) == root(v);
}
Dsu() {
for (int i = 0; i < N; ++i) t[i] = i;
}
} dsu1, dsu2;
void dfs(int u, int p = -1) {
vis[u] = 1;
tin[u] = ++tt;
low[u] = tin[u];
for (auto v : g[u]) {
if (v == p) continue;
if (vis[v]) {
low[u] = min(low[u], tin[v]);
} else {
dfs(v, u);
low[u] = min(low[u], low[v]);
if (low[v] > tin[u] && !dsu2.same(u, v)) cout << u << " " << v << "\n";
}
}
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cin >> n >> m;
int a, b;
for (int i = 1; i <= m; ++i) {
cin >> a >> b;
if (dsu1.same(a, b) && dsu2.same(a, b)) continue;
g[a].push_back(b);
g[b].push_back(a);
if (dsu1.same(a, b)) {
dsu2.merge(a, b);
} else {
dsu1.merge(a, b);
}
}
for (int i = 1; i <= n; ++i) if (!vis[i]) dfs(i);
return 0;
}
