#include <bits/stdc++.h>
#define endl '\n'
#define int long long
#define lint long long
#define pii pair<int,int>
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
#define SZ(v) ((int)v.size())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
#define MINF(a) memset(a,0x3f,sizeof(a))
#define POW(n) (1LL<<(n))
#define POPCNT(n) (__builtin_popcount(n))
#define IN(i,a,b) (a <= i && i <= b)
using namespace std;
template <typename T> inline bool CHMIN(T& a,T b) { if(a>b) { a=b; return 1; } return 0; }
template <typename T> inline bool CHMAX(T& a,T b) { if(a<b) { a=b; return 1; } return 0; }
template <typename T> inline void SORT(T& a) { sort(ALL(a)); }
template <typename T> inline void REV(T& a) { reverse(ALL(a)); }
template <typename T> inline void UNI(T& a) { sort(ALL(a)); a.erase(unique(ALL(a)),a.end()); }
template <typename T> inline T LB(vector<T>& v, T a) { return *lower_bound(ALL(v),a); }
template <typename T> inline int LBP(vector<T>& v, T a) { return lower_bound(ALL(v),a) - v.begin(); }
template <typename T> inline T UB(vector<T>& v, T a) { return *upper_bound(ALL(v),a); }
template <typename T> inline int UBP(vector<T>& v, T a) { return upper_bound(ALL(v),a) - v.begin(); }
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> istream& operator>> (istream& is, pair<T1,T2>& p) { is >> p.first >> p.second; return is; }
template <typename T> ostream& operator<< (ostream& os, const vector<T>& v) { REP(i,v.size()) { if (i) os << " "; os << v[i]; } return os; }
template <typename T> istream& operator>> (istream& is, vector<T>& v) { for(T& in : v) is >> in; return is; }
template <typename T = int> vector<T> make_v(size_t a) { return vector<T>(a); }
template <typename T, typename... Ts> auto make_v(size_t a, Ts... ts) { return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...)); }
template <typename T, typename V> typename enable_if<is_class<T>::value == 0>::type fill_v(T &t, const V &v) { t = v; }
template <typename T, typename V> typename enable_if<is_class<T>::value != 0>::type fill_v(T &t, const V &v) { for(auto &e : t) fill_v(e,v); }
const lint MOD = 1000000007;
const lint INF = 0x3f3f3f3f3f3f3f3f;
const double EPS = 1e-10;

using UnweightedGraph = vector<vector<int>>;

struct LowLink {
    vector<pair<int, int>> brs; // 橋
    vector<int> aps; // 関節点

    const UnweightedGraph &g;
    vector<int> ord, low;

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

    void dfs(int u, int &k, int p = -1) {
        low[u] = ord[u] = k++;

        // 関節点の判定に使用
        int num_of_child = 0;
        bool exist = false;

        for (auto &v : g[u]) if (v != p) {
            if (ord[v] >= 0) {
                low[u] = min(low[u], ord[v]);   // back edge
                continue;
            }
            dfs(v, k, u);
            low[u] = min(low[u], low[v]);   // forward edge
            if (ord[u] < low[v]) brs.emplace_back(min(u, v), max(u, v));
            if (ord[u] <= low[v]) exist = true;
            ++num_of_child;
        }
        if ((p == -1 && num_of_child > 1) || (p != -1 && exist))
            aps.emplace_back(u);
    }

    // 前処理
    void build() {
        const int n = g.size();
        ord.assign(n, -1);
        low.resize(n);
        int k = 0;
        for (int i = 0; i < n; ++i) {
            if (ord[i] < 0) dfs(i, k);
        }
        sort(brs.begin(), brs.end());
        sort(aps.begin(), aps.end());
    }
};

void _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 ll(g);
    ll.build();
    for (auto br : ll.brs) {
        cout << br << endl;
    }
}

signed main(signed argc, char **argv) {
    if (argc > 1) {
        if (strchr(argv[1], 'i'))
            freopen("input.txt", "r", stdin);
        if (strchr(argv[1], 'o'))
            freopen("output.txt", "w", stdout);
    }
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    _main();
    return 0;
}


Measured memory_bytes: 5224