#include<bits/stdc++.h>
#define pb push_back
#define F first
#define S second
#define make make_pair
using namespace std;
const int Max = 1e5 + 10;
int par[Max][2];
vector<pair<int , int>> N[Max];
int h[Max]; bool seen[Max];
vector<pair<int , int>> E;
int PAR(int a , int k)
{
if(par[a][k] == a) return a;
return par[a][k] = PAR(par[a][k] , k);
}
bool UNI(int a , int b , bool k)
{
a = PAR(a , k);
b = PAR(b , k);
if(a == b) return 0;
par[a][k] = b;
return 1;
}
int DFS(int v , int e , int p)
{
seen[v] = 1;
int mn = Max;
for(pair<int , int> u : N[v])
if(!seen[u.F]) h[u.F] = h[v] + 1 , mn = min(DFS(u.F , u.S , v) , mn);
else if(u.S != e) mn = min(mn , h[u.F]);
if(mn >= h[v]) E.pb(make(p , v));
return mn;
}
int main()
{
ios::sync_with_stdio(0) , cin.tie(0) , cout.tie(0);
int n , m; cin >> n >> m;
for(int i = 1 ; i <= n ; i++) par[i][0] = par[i][1] = i;
for(int i = 1 ; i <= m ; i++)
{
int a , b; cin >> a >> b;
if(UNI(a , b , 0) || UNI(a , b , 1)) N[a].pb(make(b , i)) , N[b].pb(make(a , i));
}
for(int v = 1 ; v <= n ; v++)
if(!seen[v])
DFS(v , 0 , v);
//cout << '\n';
for(pair<int , int> e : E)
if(e.F != e.S)cout << e.F << ' ' << e.S << '\n';
}
