#include <bits/stdc++.h>

using namespace std;

const int N = 1e5;

int n, m;
pair<int, int> edge[N + 5];
bool bridge[N + 5];
vector<pair<int, int>> e[N + 5];

int id[N + 5], low[N + 5], dfnTot, efa[N + 5];
void tarjan(int u) {
  id[u] = low[u] = ++dfnTot;
  for (auto [v, eid]: e[u])
    if (!id[v]) {
      efa[v] = eid, tarjan(v);
      if (low[v] > id[u]) bridge[eid] = 1;
      else low[u] = min(low[u], low[v]);
    } else if (eid != efa[u]) low[u] = min(low[u], id[v]);
}

int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= m; ++i) {
    auto &[u, v] = edge[i]; scanf("%d%d", &u, &v);
    e[u].emplace_back(v, i), e[v].emplace_back(u, i);
  }
  for (int i = 1; i <= n; ++i)
    if (!id[i]) tarjan(i);
  for (int i = 1; i <= m; ++i)
    if (bridge[i]) { auto [u, v] = edge[i]; printf("%d %d\n", u, v); }
}