#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<int> G[100000];
bool used[100000];
int R[100000];
void dfs(int x, int p, int r) {
R[x] = r;
for (int t : G[x]) {
if (t == p) continue;
dfs(t, x, r+1);
}
}
int T[100000];
int dfs2(int x, int p) {
for (int t : G[x]) {
if (t == p) continue;
T[x] += dfs2(t, x);
}
if (p != -1 && T[x] == 0) cout << x+1 << " " << p+1 << "\n";
int ret = T[x];
T[x] = INF;
return ret;
}
signed main() {
cin >> N >> M;
UnionFind uf1(N), uf2(N);
vector<P> backwards;
rep(i, M) {
int u, v;
cin >> u >> v;
u--, v--;
if (!uf1.same(u, v)) {
G[u].pb(v), G[v].pb(u);
uf1.unite(u, v);
}
else if (!uf2.same(u, v)) {
backwards.pb(P(u, v));
uf2.unite(u, v);
}
}
rep(i, N) R[i] = -1;
rep(i, N) if (R[i] == -1) dfs(i, -1, 0);
for (P p : backwards) {
int u = p._1, v = p._2;
if (R[u] > R[v]) swap(u, v);
T[v]++, T[u]--;
}
rep(i, N) if (T[i] != INF) dfs2(i, -1);
return 0;
}
