#include<bits/stdc++.h>
using namespace std;
using ll = int;
using pll = pair < ll, ll >;
const ll N = 1e5 + 2;
ll tin[N], timer = 1, low[N];
vector < ll > adj[N];
void euler_tour(ll node, ll par) {
tin[node] = timer;
low[node] = timer;
timer ++;
bool parent_found = false;
for ( ll nxt : adj[node]) {
if ( nxt == par && parent_found == false) {
parent_found = true;
continue;
}
if ( tin[nxt] > 0) {
low[node] = min(low[node], tin[nxt]);
continue;
}
euler_tour(nxt, node);
low[node] = min(low[node], low[nxt]);
if ( low[nxt] > tin[node]) {
cout << node << " " << nxt << endl;
}
}
}
ll ataman[N];
ll Get(ll x) {
if ( x == ataman[x]) return x;
return ataman[x] = Get(ataman[x]);
}
void Unite(ll x, ll y) {
x = Get(x);
y = Get(y);
if (x == y) return ;
if ( x > y) swap(x,y);
ataman[x] = y;
}
int main() {
ll n, m, r, x, y, i, j, ans, t;
cin >> n >> m;
for (i = 1; i <= n; i ++) ataman[i] = i;
for (i = 1; i <= m; i ++) {
cin >> x >> y;
if ( Get(x) == Get(y)) continue;
adj[x].push_back(y);
adj[y].push_back(x);
}
for (i = 1; i <= n; i ++) {
if ( tin[i] == 0) euler_tour(i, -1);
}
}
