/* Author: goats_9 */
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
class DSU {
int n;
vector<int> e;
public:
DSU (int _n) : n(_n), e(n, -1) {}
int get(int i) { return (e[i] < 0) ? i : (e[i] = get(e[i])); }
bool unite(int i, int j) {
i = get(i), j = get(j);
if (i == j) return false;
if (e[i] > e[j]) swap(i, j);
e[i] += e[j];
e[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);
int timer = 0;
auto dfs = [&] (auto&& self, int u, int p) -> int {
num[u] = timer++;
int low = num[u];
bool par = false;
for (int v : g[u]) {
if (v == p && !par) {
par = true;
continue;
}
if (num[v] == -1) {
int z = self(self, v, u);
low = min(low, z);
if (z > num[u]) cout << u + 1 << ' ' << v + 1 << '\n';
} else low = min(low, num[v]);
}
return low;
};
for (int i = 0; i < n; i++) if (num[i] == -1) dfs(dfs, i, -1);
return 0;
}
