#include <bits/stdc++.h>

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

//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;
    }
};
vector<Node> v;

//边双模板
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++;
}

int dfn[N], low[N], stk[N], timestamp, top;
int n, m;

void tarjan(int u, int from) {
    dfn[u] = low[u] = ++timestamp;
    stk[++top] = u;

    for (int i = h[u]; ~i; i = ne[i]) {
        int j = e[i];
        if (!dfn[j]) {
            tarjan(j, i); // j:点，i:哪条边
            low[u] = min(low[u], low[j]);
            if (dfn[u] < low[j]) v.push_back({u, j});
        } else if (i != (from ^ 1))
            low[u] = min(low[u], dfn[j]);
    }
}

int main() {
#ifndef ONLINE_JUDGE
    freopen("P1656.in", "r", stdin);
#endif

    scanf("%d %d", &n, &m);
    memset(h, -1, sizeof h);
    while (m--) {
        int a, b;
        scanf("%d %d", &a, &b);
        if (a != b) add(a, b), add(b, a);
    }

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

    //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;
}