#include <bits/stdc++.h>
using namespace std;
#define all(v) v.begin(),v.end()
#define pb push_back
#define ll long long
#define ld long double
#define fi first
#define se second
#define mk make_pair
typedef pair<int,int> pii;
const int maxn = 1e5 + 10;
int i,n,t,m,low[maxn],tim[maxn],u,v;
vector<int> adj[maxn];
struct DSU
{
int p[maxn];
DSU(int n)
{
for(int i = 1;i<=n;i++)p[i] = i;
}
int fi(int i)
{
while(i != p[i])i = p[i] = p[p[i]];
return i;
}
bool unite(int u,int v)
{
u = fi(u);
v = fi(v);
if(u == v)return 0;
p[v] = u;
return 1;
}
};
void dfs(int i,int pa)
{
tim[i] = low[i] = ++t;
bool ch = 0;
for(const int &k : adj[i])
{
if(k == pa && !ch)
{
ch = 1;
continue;
}
if(tim[k])low[i] = min(low[i],tim[k]);
else
{
dfs(k,i);
low[i] = min(low[i],low[k]);
if(low[k] == tim[k])cout<<i<<' '<<k<<'\n';
}
}
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cin>>n>>m;
DSU a(n),b(n);
while(m--)
{
cin>>u>>v;
if(a.unite(u,v) || b.unite(u,v))
{
adj[u].pb(v);
adj[v].pb(u);
}
}
for(i = 1;i<=n;i++)
{
if(!tim[i])
{
dfs(i,0);
}
}
return 0;
}
