//#pragma GCC optimize("Ofast", "unroll-loops")
//#pragma GCC target("sse", "sse2", "sse3", "ssse3", "sse4")
#include <bits/stdc++.h>
#define all(a) a.begin(),a.end()
#define len(a) (int)(a.size())
#define mp make_pair
#define pb push_back
#define fir first
#define sec second
#define fi first
#define se second
using namespace std;
typedef pair<int, int> pii;
typedef long long ll;
typedef long double ld;
template<typename T>
bool umin(T &a, T b) {
if (b < a) {
a = b;
return true;
}
return false;
}
template<typename T>
bool umax(T &a, T b) {
if (a < b) {
a = b;
return true;
}
return false;
}
#ifdef KIVI
#define DEBUG for (bool _FLAG = true; _FLAG; _FLAG = false)
#define LOG(...) print(#__VA_ARGS__" ::", __VA_ARGS__) << endl
template <class ...Ts> auto &print(Ts ...ts) { return ((cerr << ts << " "), ...); }
#else
#define DEBUG while (false)
#define LOG(...)
#endif
const int max_n = 1e5 + 11, inf = 1000111222;
struct dsu {
public:
int n;
vector <int> p;
inline void make_set (int v) {
p[v] = v;
}
dsu (int n) : n(n) {
p.resize(n);
for (int i = 0; i < n; i++) {
make_set(i);
}
}
inline int get (int v) {
if (p[v] == v) return v;
return p[v] = get(p[v]); /// compressing path
}
inline bool unite (int a, int b) {
a = get(a);
b = get(b);
if (a == b) return false;
p[a] = b;
return true;
}
};
vector <int> edge[max_n];
pii ee[max_n];
const int C = 1e5 / 2;
int tin[max_n], tout[max_n], timer, n;
bool bad[max_n];
inline void dfs (int v, int prv = inf) {
tin[v] = tout[v] = timer++;
for (int id : edge[v]) {
if (id < 0) {
id = -id - 1;
if (id == prv) {
continue;
}
int to = v ^ ee[id].first ^ ee[id].second;
if (tin[to]) {
umin(tout[v], tin[to]);
bad[id] = 1;
}
else {
dfs(to, id);
umin(tout[v], tout[to]);
if (id < n && tout[to] <= tin[v]) {
bad[id] = 1;
}
}
}
else {
int to = id;
if (-to - 1 == prv) {
continue;
}
// int to = v ^ ee[id].first ^ ee[id].second;
if (tin[to]) {
umin(tout[v], tin[to]);
// bad[id] = 1;
}
else {
dfs(to, -to - 1);
umin(tout[v], tout[to]);
// if (id < n && tout[to] <= tin[v]) {
// bad[id] = 1;
// }
}
}
}
}
int main() {
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);
int m;
cin >> n >> m;
dsu t(n);
int num = 0;
int id = 0;
for (int i = 0, u, v; i < m; ) {
int r = min(i + C, m);
for (int j = 0; j < n; j++) {
edge[j].clear();
}
for (int j = 0; j < id; j++) {
edge[ee[j].first].pb(-(j + 1));
edge[ee[j].second].pb(-(j + 1));
}
while (i < r) {
cin >> u >> v;
--u, --v;
if (t.unite(u, v)) {
edge[u].pb(-(id + 1));
edge[v].pb(-(id + 1));
ee[id++] = make_pair(u, v);
}
else {
edge[u].pb(v);
edge[v].pb(u);
}
++i;
}
for (int j = 0; j < n; j++) tin[j] = 0;
timer = 1;
for (int j = 0; j < n; j++) {
if (!tin[j]) {
dfs(j);
}
}
}
for (int i = 0; i < id; i++) {
if (!bad[i]) {
cout << ee[i].first + 1 << ' ' << ee[i].second + 1 << '\n';
}
}
}
