#include<bits/stdc++.h>
using namespace std;
struct UnionFind{
vector<int> par;
UnionFind(int n){
par.resize(n);
iota(par.begin(),par.end(),0);
}
int find(int i){
if(par[i] == i) return i;
else return par[i] = find(par[i]);
}
void unite(int i, int j){
i = find(i); j = find(j);
par[i] = j;
}
};
stack<int> occ;
bool DFS(int v, int p, int t, vector<set<int>>& adj, UnionFind& uf2){
if(uf2.find(v) == uf2.find(t)){
occ.push(v);
return true;
}
bool onPath = false;
for(auto u : adj[v]){
if(u == p) continue;
bool ans = DFS(u,v,t,adj, uf2);
onPath |= ans;
}
if(onPath){
occ.push(v);
}
return onPath;
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
int n, m;
cin >> n >> m;
UnionFind ufC(n);
UnionFind uf2(n);
vector<set<int>> adjB(n);
set<pair<int,int>> bridges;
for(int k = 0; k < m; k++){
int a,b;
cin >> a >> b;
a--;b--;
if(uf2.find(a) == uf2.find(b)){
continue;
}else if(uf2.find(a) != uf2.find(b) && ufC.find(a) != ufC.find(b)){
// add a new bridge
adjB[a].insert(b);
adjB[b].insert(a);
ufC.unite(a,b);
bridges.insert({a,b});
}else if(uf2.find(a) != uf2.find(b) && ufC.find(a) == ufC.find(b)){
// do a DFS on the bridge tree and return the path of bridges
// in the 2CC
DFS(a,a,b,adjB,uf2);
// erase the path
int u = occ.top();occ.pop();
while(occ.size()){
int w = occ.top(); occ.pop();
uf2.unite(w,u);
bridges.erase({w,u});
bridges.erase({u,w});
u = w;
}
}
}
for(auto p : bridges){
cout << p.first+1 << " "<< p.second+1 << "\n";
}
}
