#include <bits/stdc++.h>
#define task "BriantheCrab"
#define pii pair <int, int>
#define fi first
#define se second
#define szf sizeof
#define sz(s) (int)((s).size())
using namespace std;
template <class T> void mini (T &t, T f) {if (t > f) t = f;}
template <class T> void maxi (T &t, T f) {if (t < f) t = f;}
const int maxN = 1e5 + 5;
const int maxM = 6e6 + 5;
int n, m;
int timeDfs = 0;
int low[maxN], num[maxN];
struct Edge {
int to, nxt, id;
} edges[maxM * 2];
int head[maxN], edgeCnt = 0;
vector <pii> bridges;
void add_edge(int u, int v, int id) {
edges[edgeCnt] = {v, head[u], id};
head[u] = edgeCnt++;
}
void dfs(int u, int parent, int parentEdgeId) {
num[u] = low[u] = ++timeDfs;
for (int i = head[u]; i != -1; i = edges[i].nxt) {
int v = edges[i].to;
int id = edges[i].id;
if (id == parentEdgeId) continue;
if (num[v]) {
mini(low[u], num[v]);
} else {
dfs(v, u, id);
mini(low[u], low[v]);
if (low[v] > num[u]) {
bridges.push_back({min(u, v), max(u, v)});
}
}
}
}
void solve() {
memset(head, -1, sizeof head);
cin >> n >> m;
for (int i = 1; i <= m; i++) {
int u, v;
cin >> u >> v;
add_edge(u, v, i);
add_edge(v, u, i);
}
for (int i = 1; i <= n; i++) {
if (num[i] == 0) {
dfs(i, i, -1);
}
}
for (auto [x, y] : bridges) {
cout << x << ' ' << y << '\n';
}
return;
}
signed main() {
cin.tie(nullptr)->sync_with_stdio(false);
if (fopen(task".inp", "r")) {
freopen(task".inp", "r", stdin);
freopen(task".out", "w", stdout);
}
int t = 1;
//cin >> t;
while (t--) {
solve();
}
return 0;
}
// thfdgb
