//In the name of Allah
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
#define X first
#define Y second
typedef pair < int , int > pii;
const int N = 1e5 + 10;
int par[2][N];
bitset < N > mark;
vector < pii > adj[N];
int getPar(int t, int v){
return par[t][v] == v ? v : par[t][v] = getPar(t, par[t][v]);
}
bool merge(int t, int u, int v){
u = getPar(t, u); v = getPar(t, v);
if (u == v)
return false;
par[t][u] = v;
return true;
}
void DFS(int v, int p = -1){
mark[v] = 1;
par[1][v] = N; //dp[v] = N;
for (pii e : adj[v]){
int u = e.X, id = e.Y;
if (id == p)
continue;
if (mark[u])
par[1][v] = min(par[1][v], par[0][u]); //dp[v] = min(dp[v], h[u]);
else{
par[0][u] = par[0][v] + 1; //h[u] = h[v] + 1;
DFS(u, id);
par[1][v] = min(par[1][v], par[1][u]); //dp[v] = min(dp[v], dp[u]);
if (par[0][v] < par[1][u]) //(h[v] < dp[u])
cout << u << ' ' << v << '\n';
}
}
}
int main(){
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n, m;
cin >> n >> m;
for (int i = 0; i < N; i ++)
par[0][i] = par[1][i] = i;
for (int i = 0; i < m; i ++){
int u, v;
cin >> u >> v;
if (merge(0, u, v)){
adj[u].pb(mp(v, i));
adj[v].pb(mp(u, i));
}
else if (merge(1, u, v)){
adj[u].pb(mp(v, i));
adj[v].pb(mp(u, i));
}
}
memset(par, 0, sizeof par);
for (int v = 1; v <= n; v ++)
if (!mark[v])
DFS(v);
return 0;
}
