// Cao Quang Hung
#include <cassert>
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
using namespace std;
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define pii pair<int,int>
#define pll pair<long long , long long>
#define vi vector<int>
#define vpii vector<pii>
#define SZ(x) ((int)(x.size()))
#define fi first
#define se second
#define IN(x,y) ((y).find((x))!=(y).end())
#define ALL(t) t.begin(),t.end()
#define FOREACH(i,t) for (typeof(t.begin()) i=t.begin(); i!=t.end(); i++)
#define REP(i,a,b) for(int (i)=(a);(i)<=(b);++i)
#define REPD(i,a,b) for(int (i)=(a); (i)>=(b);--i)
#define FOR(i, n) for (int (i) = 0; (i) < (n); ++(i))
#define dem(x) __builtin_popcount(x)
#define Mask(x) (1LL << (x))
#define BIT(x, i) ((x) >> (i) & 1)
#define ln '\n'
#define io_faster ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
///mt19937 rnd(time(0));
const int INF = 1e9 , mod = 1e9 + 7;
template <class T1, class T2>
inline T1 mul(T1& x, const T2 &k){ return x = (1LL * x * k) % mod; }
template <class T1 , class T2>
inline T1 pw(T1 x, T2 k){T1 res = 1; for (; k ; k >>= 1){ if (k & 1) mul(res, x); mul(x, x); } return res;}
template <class T>
inline bool minimize(T &x, const T &y){ if (x > y){x = y; return 1;} return 0; }
template <class T>
inline bool maximize(T &x, const T &y){ if (x < y){x = y; return 1;} return 0; }
template <class T>
inline void add(T &x , const T &y){ if ((x += y) >= mod) x -= mod; }
template <class T>
inline T product (const T &x , const T &y) { return 1LL * x * y % mod; }
#define PROB "a"
void file(){
if(fopen(PROB".inp", "r")){
freopen(PROB".inp","r",stdin);
freopen(PROB".out","w",stdout);
}
}
void sinh_(){
// srand(time(0));
// freopen(PROB".inp" , "w" , stdout);
// int n;
}
typedef long long ll;
typedef double db;
const int N = 1e5 + 1;
int n, m, u, v;
int par[N][17], depth[N], a[N] = {};
vi adj[N];
vpii Edge;
struct DSU{
int par[N];
int root(int x) {
if (x == par[x]) return x;
return par[x] = root(par[x]);
}
bool unite(int u, int v) {
u = root(u), v = root(v);
if (u == v) return 0;
par[v] = u;
return 1;
}
void init() {
REP(i, 1, n) par[i] = i;
}
} oneE, twoE;
void readip(){
cin >> n >> m;
oneE.init();
twoE.init();
FOR(i, m) {
cin >> u >> v;
if (oneE.unite(u, v)) {
adj[u].eb(v);
adj[v].eb(u);
}
else if (twoE.unite(u, v)) Edge.eb(u, v);
}
}
void dfs_tree(int u, int p) {
for (int &v : adj[u]) if (v != p) {
depth[v] = depth[u] + 1;
par[v][0] = u;
REP(i, 1, 16) par[v][i] = par[par[v][i - 1]][i - 1];
dfs_tree(v, u);
}
}
int Lca(int u, int v) {
if (depth[u] > depth[v]) swap(u, v);
int dif = depth[v] - depth[u];
REP(i, 0, 16) if (BIT(dif, i)) v = par[v][i];
if (u == v) return u;
REPD(i, 16, 0) if (par[v][i] != par[u][i])
v = par[v][i] , u = par[u][i];
return par[u][0];
}
void dfs(int u, int p) {
for (int &v : adj[u]) if (v != p) {
dfs(v, u);
if (a[v] == 0)
cout << u << ' ' << v << ln;
else
a[u] += a[v];
}
}
void solve(){
REP(i, 1, n) if (oneE.root(i) == i) depth[i] = 0, dfs_tree(i, -1);
for (const auto &[u, v] : Edge) {
int anc = Lca(u, v);
++a[u], ++a[v];
a[anc] -= 2;
}
REP(i, 1, n) if (oneE.root(i) == i)
dfs(i, -1);
}
int main(){
sinh_();
io_faster
file();
int t = 1;
// cin >> t;
while (t--){
readip();
solve();
}
}
