#include <bits/stdc++.h>
#include <cmath>

using namespace std;
typedef long long ll;
//typedef unsigned long long ll;

#define rep(i, n) for (int i = 0; i < (n); ++i)
//#define rep(i, n) for (ll i = 0; i < (n); ++i)
//#define sz(x) ll(x.size())
//typedef pair<ll, int> P;
typedef pair<ll, ll> P;
//const double INF = 1e10;
const ll INF = LONG_LONG_MAX / 100;
//const ll INF = (1ll << 31) - 1;
//const ll INF = 1e15;
const ll MINF = LONG_LONG_MIN;
//const int INF = INT_MAX / 10;
#define cmin(x, y) x = min(x, y)
#define cmax(x, y) x = max(x, y)
//typedef pair<int, int> P;
//typedef pair<double, double> P;

bool contain(set<P> &s, P a) { return s.find(a) != s.end(); }

//ifstream myfile("C:\\Users\\riku\\Downloads\\0_00.txt");
//ofstream outfile("log.txt");
//outfile << setw(6) << setfill('0') << prefecture << setw(6) << setfill('0') << rank << endl;
// std::cout << std::bitset<8>(9);
const int mod = 1000000007;
typedef priority_queue<long long, vector<long long>, greater<long long>> PQ_ASK;


void print_line(vector<string> &line) {
    if (line.size() == 0ll) {
        cout << endl;
        return;
    }
    for (ll i = 0; i < line.size(); i++) {
        cout << line[i];
        if (i == line.size() - 1) cout << endl;
        else cout << ' ';
    }
}


template<typename T>
struct edge {
    int src, to;
    T cost;

    edge(int to, T cost) : src(-1), to(to), cost(cost) {}

    edge(int src, int to, T cost) : src(src), to(to), cost(cost) {}

    edge &operator=(const int &x) {
        to = x;
        return *this;
    }

    operator int() const { return to; }
};

template<typename T>
using Edges = vector<edge<T> >;
template<typename T>
using WeightedGraph = vector<Edges<T> >;
using UnWeightedGraph = vector<vector<int> >;
template<typename T>
using Matrix = vector<vector<T> >;

template<typename G>
struct LowLink {
    const G &g;
    vector<int> used, ord, low;
    vector<int> articulation;
    vector<pair<int, int> > bridge;

    LowLink(const G &g) : g(g) {}

    int dfs(int idx, int k, int par) {
        used[idx] = true;
        ord[idx] = k++;
        low[idx] = ord[idx];
        bool is_articulation = false;
        int cnt = 0;
        for (auto &to : g[idx]) {
            if (!used[to]) {
                ++cnt;
                k = dfs(to, k, idx);
                low[idx] = min(low[idx], low[to]);
                is_articulation |= ~par && low[to] >= ord[idx];
                if (ord[idx] < low[to]) bridge.emplace_back(minmax(idx, (int) to));
            } else if (to != par) {
                low[idx] = min(low[idx], ord[to]);
            }
        }
        is_articulation |= par == -1 && cnt > 1;
        if (is_articulation) articulation.push_back(idx);
        return k;
    }

    virtual void build() {
        used.assign(g.size(), 0);
        ord.assign(g.size(), 0);
        low.assign(g.size(), 0);
        int k = 0;
        for (int i = 0; i < g.size(); i++) {
            if (!used[i]) k = dfs(i, k, -1);
        }
    }
};

int main() {
    int v, e;
    cin >> v >> e;

    UnWeightedGraph g(v);

    rep(i, e) {
        int s, t;
        cin >> s >> t;
        g[s].push_back(t);
        g[t].push_back(s);
    }

    LowLink<UnWeightedGraph> lowlink(g);
    lowlink.build();
    sort(lowlink.bridge.begin(), lowlink.bridge.end());
    for (auto &a : lowlink.bridge) printf("%d %d\n", a.first, a.second);
}





Measured memory_bytes: 4760