#include<bits/stdc++.h>
using namespace std;
using i64 = long long;
#define int i64
#define vi vector<int>
#define vvi vector<vi>
#define vb vector<bool>
#define pii pair<int, int>
#define fi first
#define se second
#define sz(x) (int)(x).size()
struct DSU{
vi par, size_;
DSU(int n) : par(n), size_(n, 1) {
iota(par.begin(), par.end(), 0ll);
}
inline int find_set(int a){
return (par[a] == a ? a : par[a] = find_set(par[a]));
}
inline bool unite(int a, int b){
a = find_set(a), b = find_set(b);
if(a == b) return false;
if(size_[a] < size_[b]) swap(a, b);
par[b] = a;
size_[a] += size_[b];
return true;
}
inline bool same_set(int a, int b){
return find_set(a) == find_set(b);
}
};
inline void solve(){
int n, m, a, b;
cin >> n >> m;
vvi adj(n);
DSU cc(n), tcc(n);
for(int i = 0; i < m; i++){
cin >> a >> b;
a--, b--;
if(cc.unite(a, b)){
adj[a].emplace_back(b);
adj[b].emplace_back(a);
}
else if(tcc.unite(a, b)){
adj[a].emplace_back(b);
adj[b].emplace_back(a);
}
}
vi tin(n, -1), low(n, -1);
int timer = 0;
vector<pii> ans;
function<void(int, int)> dfs = [&](int v, int p) -> void {
tin[v] = low[v] = ++timer;
for(int &u : adj[v]){
if(u == p) continue;
if(tin[u] != -1){
low[v] = min(low[v], tin[u]);
}
else{
dfs(u, v);
low[v] = min(low[v], low[u]);
}
}
if(low[v] == tin[v] && p != -1){
ans.emplace_back(v, p);
}
return;
};
for(int i = 0; i < n; i++){
if(tin[i] == -1){
dfs(i, -1);
}
}
for(int i = 0; i < sz(ans); i++){
cout << ans[i].fi + 1 << " " << ans[i].se + 1 << "\n";
}
return;
}
signed main(){
ios_base::sync_with_stdio(false); cin.tie(0);
int t = 1;
//cin >> t;
while(t--){
solve();
}
return 0;
}
