#include <bits/stdc++.h>

using namespace std;

const int N = 5e5 + 10, M = 4e6 + 10;

//链式前向星
int e[M], h[N], idx, w[M], ne[M];
void add(int a, int b, int c = 0) {
    e[idx] = b, ne[idx] = h[a], w[idx] = c, h[a] = idx++;
}

//割边
struct Node {
    int x, y;
    bool const operator<(const Node &t) const {
        if (x == t.x) return y < t.y;
        return x < t.x;
    }
};

int dfn[N], low[N], timestamp, root;
vector<Node> v;

void tarjan(int u, int fa) {
    dfn[u] = low[u] = ++timestamp;
    int son = 0;
    for (int i = h[u]; ~i; i = ne[i]) {
        int j = e[i];
        if (j == fa) continue;
        if (!dfn[j]) {
            son++;
            tarjan(j, u);
            low[u] = min(low[u], low[j]);
            //记录割边
            if (low[j] > dfn[u]) v.push_back({u, j});
        }
        low[u] = min(low[u], dfn[j]);
    }
}

int n, m;
int main() {
//文件输入输出
#ifndef ONLINE_JUDGE
    freopen("P1656.in", "r", stdin);
#endif
    memset(h, -1, sizeof h);
    scanf("%d %d", &n, &m);
    while (m--) {
        int a, b;
        scanf("%d %d", &a, &b);
        if (a != b) add(a, b), add(b, a);
    }

    for (root = 1; root <= n; root++)
        if (!dfn[root]) tarjan(root, root);

    //要求先按a排序，然后按b排序
    sort(v.begin(), v.end());
    for (auto i : v) printf("%d %d\n", i.x, i.y);
    return 0;
}