#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
const int maxn = 1e5 + 20;
struct dsu
{
int p[maxn];
dsu()
{
memset(p , -1 , sizeof p);
}
int root(int v)
{
return (p[v] < 0? v : p[v] = root(p[v]));
}
bool merge(int v , int u)
{
v = root(v) , u = root(u);
if(v == u)
return 0;
if(-p[v] < -p[u])
swap(v , u);
p[v] += p[u];
p[u] = v;
return 1;
}
};
dsu tree , tc;
int dp[maxn] , h[maxn];
bool visited[maxn];
vector<int> adj[maxn];
void dfs(int v , int p = -1)
{
visited[v] = 1;
dp[v] = h[v];
bool seen = 0;
for(auto u : adj[v])
{
if(!visited[u])
{
h[u] = h[v] + 1;
dfs(u , v);
dp[v] = min(dp[v] , dp[u]);
}
else if(h[u] < h[v] - 1 || seen)
dp[v] = min(dp[v] , h[u]);
seen |= (u == p);
}
if(p != -1 && dp[v] >= h[v])
cout << v + 1 << " " << p + 1 << endl;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n , m;
cin >> n >> m;
for(int i = 0; i < m; i++)
{
int a , b;
cin >> a >> b;
a-- , b--;
if(tree.merge(a , b) || tc.merge(a , b))
adj[a].pb(b) , adj[b].pb(a);
}
for(int i = 0; i < n; i++)
if(!visited[i])
dfs(i);
}
