#include <bits/stdc++.h>
using namespace std;
const int nmax = 1e5 + 1, mod = 1e6 + 7;
/*
struct DSU {
int root[nmax], sz[nmax];
void init(int n) {
for(int i = 1; i <= n; i++) {
root[i] = i;
sz[i] = 1;
}
}
int find(int a) {
if(root[a] == a) {
return a;
}
return root[a] = find(root[a]);
}
void unite(int a, int b) {
assert(a != b);
if(sz[a] > sz[b]) {
swap(a, b);
}
root[a] = b;
sz[b] += sz[a];
}
} d1, d2;*/
vector<pair<int, int>> adj[nmax];
int low[nmax];
int t[nmax];
bool f[nmax];
int ind, comp, timer = 0;
void dfs(int v, int par){
f[v] = true;
low[v] = t[v] = ++timer;
for(int i = 0; i < adj[v].size(); ++i){
int u = adj[v][i].first;
int e = adj[v][i].second;
if(e == par) continue;
if(!f[u]){
dfs(u,e);
low[v] = min(low[v],low[u]);
if(low[u] > t[v]) printf("%d %d\n",u,v);
}
else low[v] = min(low[v],t[u]);
}
}
int32_t main(){
ios_base::sync_with_stdio(0);cin.tie(0);
int n, m;
cin >> n >> m;
//d1.init(n), d2.init(n);
int cnt = 0;
for(int i = 1; i <= m; i++) {
int a, b;
cin >> a >> b;
cnt++;
adj[a].push_back({b, cnt});
adj[b].push_back({a, cnt});
}
// assert(cnt < n * 2 + 1);
for(int i = 1; i <= n; i++) {
if(!f[i]) {
dfs(i, 0);
}
}
return 0;
}
