//#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, cnt;
inline void make_set (int v) {
p[v] = v;
}
dsu (int n) : n(n) {
p.resize(n);
cnt.assign(n, 1);
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;
if (cnt[a] > cnt[b]) {
swap(a, b);
}
p[a] = b;
cnt[b] += cnt[a];
return true;
}
};
const int max_m = 6e6 + 11;
int a[max_m], b[max_m];
vector <int> edge[max_n];
const int L = 10;
int up[max_n][L + 1];
int timer = 0;
int tin[max_n], tout[max_n];
bool used[max_n];
inline void dfs_lca (int v, int p = -1) {
tin[v] = timer++;
used[v] = 1;
up[v][0] = p == -1 ? v : p;
for (int i = 1; i <= L; i++) {
up[v][i] = up[up[v][i - 1]][i - 1];
}
for (int to : edge[v]) {
if (to == p) continue;
dfs_lca(to, v);
}
tout[v] = timer;
}
inline bool upper (int a, int b) {
return tin[a] <= tin[b] && tout[b] <= tout[a];
}
inline int lca (int a, int b) {
if (upper(a, b)) return a;
if (upper(b, a)) return b;
for (int i = L; i >= 0; i--) {
while (!upper(up[a][i], b)) {
a = up[a][i];
}
}
return up[a][0];
}
int down[max_n];
inline void go (int v, int p = -1) {
used[v] = false;
for (int to : edge[v]) {
if (to == p) {
continue;
}
go(to, v);
if (!down[to]) {
cout << v + 1 << ' ' << to + 1 << '\n';
}
down[v] += down[to];
}
// if (down[v]) {
// cout << p + 1 << ' ' << v + 1 << '\n';
// }
}
int main() {
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);
int n, m;
cin >> n >> m;
dsu t(n);
int num = 0;
for (int i = 0, u, v; i < m; i++) {
cin >> u >> v;
--u, --v;
if (t.unite(u, v)) {
edge[u].pb(v);
edge[v].pb(u);
}
else {
a[num] = u;
b[num] = v;
++num;
}
}
for (int i = 0; i < n; i++) {
if (!used[i]) {
dfs_lca(i);
}
}
for (int i = 0; i < num; i++) {
int v = lca(a[i], b[i]);
++down[a[i]];
++down[b[i]];
down[v] -= 2;
}
for (int i = 0; i < n; i++) {
if (used[i]) {
go(i);
}
}
}
