//In the name of god
#include <bits/stdc++.h>
#define F first
#define S second
#define pb push_back
#define debug(x) cerr << #x << " : " << x << "\n"
#define use_file freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout);
using namespace std;
typedef int ll;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef string str;
const ll maxn = 1e5 + 5;
const ll mod = 1e9 + 7;
ll n, m, a[maxn], b[maxn];
vector <ll> adj[maxn];
bool mrk[maxn];
ll get_a(ll v){
if(a[v] == v)return v;
a[v] = get_a(a[v]);
return a[v];
}
bool merge(ll v, ll u){
u = get_a(u);
v = get_a(v);
if(u == v)return 0;
a[v] = u;
return 1;
}
ll get_b(ll v){
if(b[v] == v)return v;
b[v] = get_b(b[v]);
return b[v];
}
bool merge2(ll v, ll u){
u = get_b(u);
v = get_b(v);
if(u == v)return 0;
b[v] = u;
return 1;
}
vector <pll> vec;
void dfs(ll v, ll p){
mrk[v] = 1;
bool bl = 0;
b[v] = a[v];
for(ll j : adj[v]){
if(mrk[j]){
if(j == p){
if(!bl)bl = 1;
else b[v] = min(b[v], a[j]);
}
else b[v] = min(b[v], a[j]);
continue;
}
a[j] = a[v] + 1;
dfs(j, v);
b[v] = min(b[v], b[j]);
}
if(a[v] == b[v] && p)vec.pb({v, p});
}
int main(){
ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
cin >> n >> m;
for(ll i = 1; i <= n; i ++){
b[i] = i;
a[i] = i;
}
for(ll i = 0; i < m; i ++){
ll u, v; cin >> u >> v;
if(merge(u, v)){
adj[u].pb(v);
adj[v].pb(u);
continue;
}
else if(merge2(u, v)){
adj[u].pb(v);
adj[v].pb(u);
}
}
for(ll i = 1; i <= n; i ++){
a[i] = 0;
b[i] = 0;
}
for(ll i = 1; i <= n; i ++){
if(!mrk[i]){
dfs(i, 0);
continue;
}
}
for(pll i : vec)cout << i.F << ' ' << i.S << '\n';
}
