/* Author: goats_9 */
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
class DSU {
int n;
vector<int> p, rank;
public:
DSU (int _n) : n(_n), p(n), rank(n) { iota(p.begin(), p.end(), 0); }
int get(int i) { return (p[i] == i) ? p[i] : (p[i] = get(p[i])); }
bool unite(int i, int j) {
i = get(i), j = get(j);
if (i == j) return false;
if (rank[i] < rank[j]) swap(i, j);
if (rank[i] == rank[j]) ++rank[i];
p[j] = i;
return true;
}
};
int main() {
cin.tie(0)->sync_with_stdio(0);
int n, m;
cin >> n >> m;
DSU dsu(n), dsu2(n);
vector<vector<int>> g(n);
for (int i = 0; i < m; i++) {
int u, v;
cin >> u >> v;
if (dsu.unite(--u, --v) || dsu2.unite(u, v)) {
g[u].push_back(v);
g[v].push_back(u);
}
}
vector<int> num(n, -1), low(n, -1);
vector<pair<int, int>> a;
int timer = 0;
auto dfs = [&] (auto&& self, int u, int p) -> void {
num[u] = low[u] = timer++;
bool par = false;;
for (int v : g[u]) {
if (v == p && !par) {
par = true;
continue;
}
if (num[v] == -1) {
self(self, v, u);
low[u] = min(low[u], low[v]);
if (low[v] > num[u]) a.emplace_back(u + 1, v + 1);
} else low[u] = min(low[u], num[v]);
}
};
for (int i = 0; i < n; i++) if (num[i] == -1) dfs(dfs, i, -1);
for (auto [x, y] : a) cout << x << ' ' << y << '\n';
return 0;
}
