#include <iostream>
#include <fstream>
#include <bitset>
#include <cassert>
#include <vector>
#define rep(i, n) for (int i=0; i<(n); i++)
#define INF 1145141919
#define pb push_back
#define _1 first
#define _2 second
using namespace std;
typedef pair<int, int> P;
struct UnionFind {
int U[100000];
UnionFind(int N) {
rep(i, N) U[i] = i;
}
int find(int x) {
if (U[x] == x) return x;
return U[x] = find(U[x]);
}
void unite(int x, int y) {
x = find(x), y = find(y);
if (x == y) return;
U[x] = y;
}
bool same(int x, int y) {
return find(x) == find(y);
}
};
int N, M;
vector<P> G[100000];
bool used[100000];
int R[100000], T[100000];
void dfs(int x, int pe, int r) {
used[x] = true;
R[x] = r;
for (P pp : G[x]) {
int t = pp._1;
if (pp._2 == pe) continue;
if (used[t]) {
if (R[x] > R[t]) T[x]++, T[t]--;
continue;
}
dfs(t, pp._2, r+1);
}
}
void dfs2(int x, int p) {
used[x] = true;
for (P pp : G[x]) {
int t = pp._1;
if (t == p || used[t]) continue;
dfs2(t, x);
T[x] += T[t];
}
if (p != -1 && T[x] == 0) cout << x+1 << " " << p+1 << "\n";
}
signed main() {
cin >> N >> M;
UnionFind uf1(N), uf2(N);
rep(i, M) {
int u, v;
cin >> u >> v;
u--, v--;
if (!uf1.same(u, v)) {
G[u].pb(P(v, i)), G[v].pb(P(u, i));
uf1.unite(u, v);
}
else if (!uf2.same(u, v)) {
G[u].pb(P(v, i)), G[v].pb(P(u, i));
uf2.unite(u, v);
}
}
rep(i, N) used[i] = false;
rep(i, N) if (!used[i]) dfs(i, -1, 0);
rep(i, N) used[i] = false;
rep(i, N) if (!used[i]) dfs2(i, -1);
return 0;
}
