#line 2 "lib/graph/lowlink.cpp"

#line 2 "lib/graph/graph.cpp"

#line 2 "lib/template.cpp"

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <cstring>
#include <functional>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
using namespace std;
using ll = long long;
using ull = unsigned long long;
using VI = vector<int>;
using VVI = vector<vector<int>>;
using VLL = vector<ll>;
using VVLL = vector<vector<ll>>;
using VB = vector<bool>;
using PII = pair<int, int>;
using PLL = pair<ll, ll>;
constexpr int INF = 1000000007;
constexpr ll INF_LL = 1'000'000'000'000'000'007;
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define newl '\n'

// loops rep(until) / rep(var, until) / rep(var, from, until) / repr (reversed order)
#define OVERLOAD3(_1, _2, _3, name, ...) name
#define rep(...) OVERLOAD3(__VA_ARGS__, REPEAT_FROM_UNTIL, REPEAT_UNTIL, REPEAT)(__VA_ARGS__)
#define REPEAT(times) REPEAT_CNT(_repeat, __COUNTER__, times)
#define REPEAT_CNT(_repeat, cnt, times) REPEAT_CNT_CAT(_repeat, cnt, times)
#define REPEAT_CNT_CAT(_repeat, cnt, times) REPEAT_FROM_UNTIL(_repeat ## cnt, 0, times)
#define REPEAT_UNTIL(name, times) REPEAT_FROM_UNTIL(name, 0, times)
#define REPEAT_FROM_UNTIL(name, from, until) for (int name = from, name ## __until = (until); name < name ## __until; name++)
#define repr(...) OVERLOAD3(__VA_ARGS__, REPR_FROM_UNTIL, REPR_UNTIL, REPEAT)(__VA_ARGS__)
#define REPR_UNTIL(name, times) REPR_FROM_UNTIL(name, 0, times)
#define REPR_FROM_UNTIL(name, from, until) for (int name = (until)-1, name ## __from = (from); name >= name ## __from; name--)

template <typename T, typename U>
bool chmin(T& var, U x) { if (var > x) { var = x; return true; } else return false; }
template <typename T, typename U>
bool chmax(T& var, U x) { if (var < x) { var = x; return true; } else return false; }
ll power(ll e, ll t, ll mod = INF_LL) {
  ll res = 1; for (; t; t >>= 1, (e *= e) %= mod) if (t & 1) (res *= e) %= mod; return res;
}
template <typename T, typename U> T divceil(T m, U d) { return (m + d - 1) / d; }
template <typename T> vector<T> make_v(size_t a, T b) { return vector<T>(a, b); }
template <typename... Ts> auto make_v(size_t a, Ts... ts) {
  return vector<decltype(make_v(ts...))>(a, make_v(ts...));
}

// debugging stuff
#define repi(it, ds) for (auto it = ds.begin(); it != ds.end(); it++)
class DebugPrint { public: template <typename T> DebugPrint& operator <<(const T& v) {
#ifdef LOCAL
    cerr << v;
#endif
return *this; } } debugos; template <typename T> DebugPrint& operator<<(DebugPrint& os, const
vector<T>& vec) { os << "{"; for (int i = 0; i < vec.size(); i++) os << vec[i] << (i + 1 ==
vec.size() ? "" : ", "); os << "}"; return os; } template <typename T, typename U> DebugPrint&
operator<<(DebugPrint& os, const map<T, U>& map_var) { os << "{"; repi(itr, map_var) { os << *
itr; itr++; if (itr != map_var.end()) os << ", "; itr--; } os << "}"; return os; } template <
typename T> DebugPrint& operator<<(DebugPrint& os, const set<T>& set_var) { os << "{"; repi(
itr, set_var) { os << *itr; itr++; if (itr != set_var.end()) os << ", "; itr--; } os << "}";
return os; } template <typename T, typename U> DebugPrint& operator<<(DebugPrint& os, const
pair<T, U>& p) { os << "(" << p.first << ", " << p.second << ")"; return os; } void dump_func(
) { debugos << newl; } template <class Head, class... Tail> void dump_func(Head &&head, Tail
&&... tail) { debugos << head; if (sizeof...(Tail) > 0) { debugos << ", "; } dump_func(forward
<Tail>(tail)...); }
#ifdef LOCAL
#define dump(...) debugos << "  " << string(#__VA_ARGS__) << ": " << "[" << to_string(__LINE__) \
<< ":" << __FUNCTION__ << "]" << newl << "    ", dump_func(__VA_ARGS__)
#else
#define dump(...) ((void)0)
#endif


#line 4 "lib/graph/graph.cpp"

struct Edge {
  int to; ll cost;
  Edge(int _to) : to(_to), cost(1) {}
  Edge(int _to, ll _cost) : to(_to), cost(_cost) {}
  operator int() const { return to; }
};

using Graph = vector<vector<Edge>>;
#line 4 "lib/graph/lowlink.cpp"

struct LowLink {
  int n, root;
  VI ord, low, par;
  VB cutv;
  LowLink(const Graph& graph, int root_ = 0)
      : n(graph.size()), root(root_), ord(n, -1), low(n), par(n, -1), cutv(n) {
    int t = 0;
    auto dfs = [&](auto f, int v) -> void {
      ord[v] = low[v] = t++;
      for (auto e : graph[v])
        if (e.to != par[v]) {
          if (ord[e.to] == -1) par[e.to] = v, f(f, e.to), chmin(low[v], low[e.to]);
          else chmin(low[v], ord[e.to]);
        }
    };
    dfs(dfs, root);
    int root_deg = 0;
    rep(i, n) root_deg += par[i] == root;
    cutv[root] = root_deg > 1;
    rep(i, n) if (i != root and par[i] != root and ord[par[i]] <= low[i]) cutv[par[i]] = true;
    dump(par);
    dump(ord);
    dump(low);
  }
  bool is_bridge(int u, int v) {
    if (u != par[v]) swap(u, v);
    assert(u == par[v]);
    return ord[u] < low[v];
  }
  bool is_bridge(int v) {
    return ord[par[v]] < low[v];
  }
  bool is_cutv(int v) { return cutv[v]; }
};
#line 2 "main.cpp"

int main() {
  cin.tie(0); ios_base::sync_with_stdio(0);

  int v, e; cin >> v >> e;
  Graph graph(v);
  rep(e) {
    int u, v; cin >> u >> v;
    graph[u].emplace_back(v);
    graph[v].emplace_back(u);
  }
  auto l = LowLink(graph);
  vector<PII> res;
  rep(i, 1, v) if (l.is_bridge(i)) res.emplace_back(minmax(l.par[i], i));
  sort(all(res));
  rep(i, res.size()) printf("%d %d\n", res[i].first, res[i].second);
}



Measured memory_bytes: 6244