#include <bits/stdc++.h>
using namespace std;
#define MAX 100100
#define LOG 17
#define ll long long
#define pii pair<int,int>
#define pll pair<ll,ll>
#define fi first
#define se second
#define all(a) (a).begin(),(a).end()
#define __buitin_popcount __builtin_popcountll
#define BIT(x,i) (((x)>>(i))&1ll)
#define MASK(i) (1ll<<(i))
template<class X,class Y> bool maximize(X &x,Y y)
{
if(x<y)
{
x=y;
return 1;
}
return 0;
}
template<class X,class Y> bool minimize(X &x,Y y)
{
if(y<x)
{
x=y;
return 1;
}
return 0;
}
const int inf=1e9+412009;
const ll INF=2e18+412009;
struct EDGE
{
int u,v;
int other(int x)
{
assert(x==u||x==v);
return u+v-x;
}
};
struct DSU
{
vector<int> par;
DSU(int n=0)
{
par.resize(n+1);
for(int i=1;i<=n;i++) par[i]=i;
}
int find_set(int a)
{
if(a==par[a]) return a;
int p=find_set(par[a]);
par[a]=p;
return p;
}
bool union_set(int a,int b)
{
a=find_set(a);
b=find_set(b);
if(b!=a)
{
par[b]=a;
return 1;
}
return 0;
}
};
EDGE edge[2*MAX];
int n,m;
vector<int> adj[MAX];
DSU dsu[2];
int low[MAX],num[MAX],dem=0;
bool used[2*MAX]={},bridge[2*MAX]={};
void dfs(int u)
{
num[u]=++dem;
low[u]=n+1;
for(int id:adj[u]) if(!used[id])
{
used[id]=1;
int v=edge[id].other(u);
if(num[v]==0)
{
dfs(v);
minimize(low[u],low[v]);
if(low[v]>num[u]) bridge[id]=1;
}
else minimize(low[u],num[v]);
}
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);cout.tie(nullptr);
cin>>n>>m;
dsu[0]=dsu[1]=DSU(n);
int cnt=0;
for(int i=1;i<=m;i++)
{
int u,v;
cin>>u>>v;
if(dsu[0].union_set(u,v)||dsu[1].union_set(u,v))
{
edge[++cnt]={u,v};
adj[u].push_back(cnt);
adj[v].push_back(cnt);
}
}
for(int i=1;i<=n;i++) if(num[i]==0)
dfs(i);
for(int i=1;i<=cnt;i++) if(bridge[i]) cout<<edge[i].u<<' '<<edge[i].v<<'\n';
return 0;
}
