#include <bits/stdc++.h>
using namespace std;
const int nx=1e5+5;
int n, m, u, v, dsu1[nx], dsu2[nx], t, rt;
vector<pair<int ,int>> d[nx];
int find1(int x)
{
if (dsu1[x]==x) return x;
return dsu1[x]=find1(dsu1[x]);
}
int find2(int x)
{
if (dsu2[x]==x) return x;
return dsu2[x]=find2(dsu2[x]);
}
void dfs(int u, int p, int pidx)
{
dsu1[u]=dsu2[u]=++t;
for (auto [v, idx]:d[u])
{
if (idx==pidx) continue;
if (!dsu1[v]) dfs(v, u, idx), dsu2[u]=min(dsu2[u], dsu2[v]);
else dsu2[u]=min(dsu2[u], dsu1[v]);
}
if (dsu1[u]==dsu2[u]&&u!=rt) cout<<u<<' '<<p<<'\n';
}
int main()
{
cin.tie(NULL)->sync_with_stdio(false);
cin>>n>>m;
for (int i=1; i<=n ;i++) dsu1[i]=dsu2[i]=i;
for (int i=1; i<=m; i++)
{
cin>>u>>v;
if (find1(u)!=find1(v))
{
dsu1[find1(u)]=find1(v);
d[u].push_back({v, i});
d[v].push_back({u, i});
}
else if (find2(u)!=find2(v))
{
dsu2[find2(u)]=find2(v);
d[u].push_back({v, i});
d[v].push_back({u, i});
}
}
for (int i=1; i<=n; i++) dsu1[i]=dsu2[i]=0;
for (int i=1; i<=n; i++) if (!dsu1[i]) rt=i, dfs(i, i, -1);
}
