// includes
#include <bits/stdc++.h>
using namespace std;

// macros
#define pb emplace_back
#define mk make_pair
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define irep(itr, st) for(auto itr = (st).begin(); itr != (st).end(); ++itr)
#define irrep(itr, st) for(auto itr = (st).rbegin(); itr != (st).rend(); ++itr)
#define whole(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define bit(n) (1LL<<(n))
// functions
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}
template <typename T> ostream &operator<<(ostream &os, const vector<T>& vec){for(int i = 0; i < vec.size(); i++){ os << vec[i]; if(i + 1 != vec.size())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){os << "(" << p.first << ", " << p.second << ")"; return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << "(" << itr->first << ", " << itr->second << ")"; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const unordered_map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << "(" << itr->first << ", " << itr->second << ")"; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
//  types
using ll = long long int;
using P = pair<int, int>;
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1000000007;
const int dx[4] = {-1, 0, 1, 0};
const int dy[4] = {0, -1, 0, 1};
// io
struct fast_io{
  fast_io(){ios_base::sync_with_stdio(false); cin.tie(nullptr); cout << fixed << setprecision(20);}
} fast_io_;

struct LowLink{
  int n;
  vector<vector<int>> edge;
  vector<int> ord, low;
  vector<int> articulation;
  vector<pair<int, int>> bridge;
  int c;
  LowLink(int n = 0): n(n){
    edge.resize(n);
    ord.resize(n);
    low.resize(n);
  }
  void adde(int u, int v){
    edge[u].push_back(v);
  }
  void dfs(int i, int p){
    ord[i] = c++;
    low[i] = ord[i];
    int cnt = 0;
    bool is_articulation = false;
    for(auto e: edge[i]){
      if(ord[e] < n){
        if(e != p)low[i] = min(low[i], ord[e]);
      }else{
        cnt++;
        dfs(e, i);
        low[i] = min(low[i], low[e]);
        if(ord[i] < low[e])bridge.emplace_back(min(i, e), max(i, e));
        if(p != -1 && ord[i] <= low[e])is_articulation = true;
      }
    }
    if(p == -1 && cnt > 1)is_articulation = true;
    if(is_articulation)articulation.push_back(i);
  }
  void build(){
    c = 0;
    fill(ord.begin(), ord.end(), n + 1);
    dfs(0, -1);
  }
};


int main(int argc, char const* argv[])
{
  int n, m; cin >> n >> m;
  LowLink lk(n);
  rep(i, m){
    int u, v; cin >> u >> v;
    lk.adde(u, v);
    lk.adde(v, u);
  }
  lk.build();
  auto v = lk.bridge;
  sort(whole(v));
  for(auto e: v){
    cout << e.first << " " << e.second << endl;
  }
  return 0;
}



Measured memory_bytes: 4480