#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;

typedef pair<int, int> Pair;

int n, m;
int low[100000];
int ord[100000];
bool used[100000];
vector<Pair> ans;
vector<int> es[100000];

void dfs(int v, int p, int &idx) {
    used[v] = true;
    low[v] = ord[v] = idx++;

    for (int i=0; i<es[v].size(); i++) {
        int u = es[v][i];
        if (!used[u]) {
            dfs(u, v, idx);
            low[v] = min(low[v], low[u]);
            if (ord[v] < low[u]) {
                int s = min(u, v);
                int t = max(u, v);
                ans.push_back(Pair(s, t));
            }
        } else if (u != p) {
            low[v] = min(low[v], ord[u]);
        }
    }
}
    

int main() {
    scanf("%d%d", &n, &m);
    for (int i=0; i<m; i++) {
        int a, b;
        scanf("%d%d", &a, &b);
        es[a].push_back(b);
        es[b].push_back(a);
    }

    int _ = 0;
    dfs(0, 0, _);

    sort(ans.begin(), ans.end());
    for (int i=0; i<ans.size(); i++) {
        printf("%d %d\n", ans[i].first, ans[i].second);
    }
}