#include <bits/stdc++.h>
#include <bits/extc++.h>
using namespace __gnu_pbds;
using namespace std;
// #pragma GCC optimize("Ofast")
// #pragma GCC optimize ("unroll-loops")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define ff first
#define sc second
#define pb push_back
#define ll long long
#define pll pair<ll, ll>
#define pii pair<int, int>
#define ull unsigned long long
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rngl(chrono::steady_clock::now().time_since_epoch().count());
// #define int long long
// #define int unsigned long long
// #define ordered_set(T) tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>
// #define ordered_multiset(T) tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>
const ll mod = 1e9 + 7;
// const ll mod = 998244353;
const ll inf = 1e9;
const ll biginf = 1e18;
const int maxN = 1e5 + 15;
int n, m;
struct dsu {
int par[maxN], sz[maxN];
void make_set() {
for (int i = 1; i <= n; i++) {
par[i] = i; sz[i] = 1;
}
}
int find_set(int v) {
if (par[v] == v) return v;
return par[v] = find_set(par[v]);
}
bool union_set(int x, int y) {
x = find_set(x);
y = find_set(y);
if (x == y) return 0;
if (sz[x] < sz[y]) swap(x, y);
par[y] = x; sz[x] += sz[y];
return 1;
}
} d1, d2;
bool used[maxN];
vector<int> g[maxN];
int in[maxN], low[maxN], tim;
void dfs(int v, int p) {
used[v] = 1;
in[v] = low[v] = ++tim;
bool skip = 0;
for (int u : g[v]) {
if (u == p && !skip) { skip = 1; continue; }
if (used[u]) low[v] = min(low[v], in[u]);
else {
dfs(u, v);
low[v] = min(low[v], low[u]);
if (low[u] > in[v]) cout << u << ' ' << v << '\n';
}
}
}
void solve() {
cin >> n >> m;
d1.make_set(); d2.make_set();
for (int i = 1; i <= m; i++) {
int x, y; cin >> x >> y;
if (d1.union_set(x, y) || d2.union_set(x, y)) {
g[x].pb(y); g[y].pb(x);
}
}
for (int i = 1; i <= n; i++)
if (!in[i]) dfs(i, -1);
}
int32_t main() {
// #ifndef ONLINE_JUDGE
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
// #endif
ios_base::sync_with_stdio(false);
cin.tie(nullptr); cout.tie(nullptr);
int t = 1;
// cin >> t;
while (t--) {
solve();
cout << '\n';
}
return 0;
}
