//Huyduocdithitp
#include<bits/stdc++.h>
typedef int ll;
#define endl '\n'
#define fi first
#define se second
#define pii pair<ll,ll>
#define N 100005
#define LOG 18
using namespace std;
// y tuong: vi len toi 1e6 canh, ta nhan thay chi can quan tam toi da 2 * n - 2 canh thoi. nhu the dam bao
// tao du cac tplt manh roi
// ta se dung 2 dsu, 1 dinh duoc noi 2 lan roi thi khong can noi them nua
const ll inf = 1e9;
bool ghuy4g;
ll n, m;
vector<ll> adj[N];
ll num[N], low[N], timeDfs;
vector<ll> par, par1;
vector<pii> g;
ll find(ll u) {
if (par[u] < 0) return u;
return par[u] = find(par[u]);
}
void join(ll u, ll v) {
u = find(u);
v = find(v);
if (u == v) return;
if (par[u] <= par[v]) {
par[u] += par[v];
par[v] = u;
}
else {
par[v] += par[u];
par[u] = v;
}
}
ll find1(ll u) {
if (par1[u] < 0) return u;
return par1[u] = find1(par1[u]);
}
void join1(ll u, ll v) {
u = find1(u);
v = find1(v);
if (u == v) return;
if (par1[u] <= par1[v]) {
par1[u] += par1[v];
par1[v] = u;
}
else {
par1[v] += par1[u];
par1[u] = v;
}
}
void dfs(ll u, ll parent) {
num[u] = low[u] = ++ timeDfs;
bool see = 0;
for (auto v : adj[u]) {
if (v == parent && see == 0) {
see = 1;
continue;
}
if (num[v]) {
low[u] = min(low[u], num[v]);
}
else {
dfs(v, u);
low[u] = min(low[u], low[v]);
if (low[v] == num[v]) {
cout << u << " " << v << endl;
}
}
}
}
void solve() {
for (int i = 1; i <= n; i ++) {
if (num[i] == 0) {
dfs(i, 0);
}
}
}
bool klinh;
signed main() {
//freopen("test.inp", "r", stdin);
//freopen("test.out", "w", stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> m;
par.resize(n + 1, -1);
par1.resize(n + 1, -1);
for (int i = 1; i <= n; i ++) {
par[i] = par1[i] = -1;
}
for (int i = 1; i <= m; i ++) {
ll u, v;
cin >> u >> v;
if (find(u) != find(v)) {
join(u, v);
g.push_back({u, v});
}
else if (find1(u) != find1(v)) {
join1(u, v);
g.push_back({u, v});
}
}
par.clear();
par1.clear();
while (g.size()) {
//cout << g.back().fi << " " << g.back().se << endl;
adj[g.back().fi].push_back(g.back().se);
adj[g.back().se].push_back(g.back().fi);
g.pop_back();
}
solve();
cerr << fabs(&klinh - &ghuy4g) / double(1024 * 1024);
return 0;
}
