#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, b) for (int i = (a); i < (b); ++i)
#define per(i, a, b) for (int i = (b - 1); i >= (a); --i)
#define trav(a, x) for (auto &a : x)
#define all(x) x.begin(), x.end()
#define sz(x) x.size()
#define pb push_back
#define debug(x) cout << #x << " = " << x << endl
#define umap unordered_map
#define uset unordered_set
typedef pair<int, int> ii;
typedef pair<int, ii> iii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<vi> vvi;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef vector<ll> vll;
typedef vector<pll> vpll;
const int INF = 1'000'000'007;
struct union_find {
int p[100001];
char rank[100001];
union_find(int n) {
rep(i, 0, n) p[i] = i;
memset(rank, 0, sizeof(rank));
}
int find_set(int i) { return p[i] == i ? i : p[i] = find_set(p[i]); }
bool same(int i, int j) { return find_set(i) == find_set(j); }
void union_set(int i, int j) {
i = find_set(i);
j = find_set(j);
if (i == j) return;
if (rank[i] < rank[j]) swap(i, j);
if (rank[i] == rank[j]) ++rank[i];
p[j] = i;
}
};
int dfs_num[100001], dfs_lo[100001], cnt = 0;
vi graph[100001];
void dfs(int u, int p) {
dfs_num[u] = dfs_lo[u] = cnt++;
trav(v, graph[u]) {
if (dfs_num[v] == -1) {
dfs(v, u);
if (dfs_num[u] < dfs_lo[v]) cout << u + 1 << ' ' << v + 1 << endl;
dfs_lo[u] = min(dfs_lo[u], dfs_lo[v]);
}
else if (v != p)
dfs_lo[u] = min(dfs_lo[u], dfs_num[v]);
else p=-1;
}
}
int main() {
cin.tie(0)->sync_with_stdio(0);
cin.exceptions(cin.failbit);
memset(dfs_num, -1, sizeof(dfs_num));
int n, m, u, v;
cin >> n >> m;
union_find uf1(n), uf2(n);
rep(i, 0, m) {
cin >> u >> v;
--u;
--v;
if(uf1.same(u,v)&&uf2.same(u,v))continue;
if (uf1.same(u, v)) {
uf2.union_set(u, v);
graph[u].pb(v);
graph[v].pb(u);
}
else {
uf1.union_set(u, v);
graph[u].pb(v);
graph[v].pb(u);
}
}
rep(i, 0, n) {
if (dfs_num[i] != -1) continue;
cnt = 0;
dfs(i,i);
}
return 0;
}
