#include <bits/stdc++.h>
using namespace std;
const int nmax = 1e5 + 1, mod = 1e6 + 7;
struct DSU {
int root[nmax];
void init(int n) {
for(int i = 1; i <= n; i++) {
root[i] = i;
}
}
int find(int a) {
if(root[a] == a) {
return a;
}
return root[a] = find(root[a]);
}
void unite(int a, int b) {
assert(a != b);
root[a] = b;
}
} d1, d2;
vector<pair<int, int>> adj[nmax];
int low[nmax];
int t[nmax];
bitset<nmax> f;
int timer = 0;
void dfs(int i, int timp) {
f[i] = 1;
t[i] = low[i] = timer++;
for(auto curr : adj[i]) {
int it = curr.first;
if(curr.second == timp) {
continue;
}
if(f[it]) {
low[i] = min(low[i], t[it]);
} else {
dfs(it, curr.second);
low[i] = min(low[i], low[it]);
if(t[i] < low[it]) {
cout << i << " " << it << '\n';
}
}
}
}
int32_t main(){
ios_base::sync_with_stdio(0);cin.tie(0);
int n, m;
cin >> n >> m;
d1.init(n), d2.init(n);
int cnt = 0;
int a, b;
for(int i = 1; i <= m; i++) {
cin >> a >> b;
if(d1.find(a) != d1.find(b)) {
cnt++;
d1.unite(d1.find(a), d1.find(b));
adj[a].push_back({b, cnt});
adj[b].push_back({a, cnt});
} else if(d2.find(a) != d2.find(b)) {
cnt++;
d2.unite(d2.find(a), d2.find(b));
adj[a].push_back({b, cnt});
adj[b].push_back({a, cnt});
}
}
assert(cnt < n * 2 + 1);
for(int i = 1; i <= n; i++) {
if(!f[i]) {
dfs(i, 0);
}
}
return 0;
}
