#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
#define trav(a, x) for(auto& a : x)
#define FOR(i, a, b) for (int i=(a); i<=(signed)(b); i++)
#define ROF(i, a, b) for (int i=(a); i>=(signed)(b); i--)
#define F0R(i, a) for (int i=0; i<(signed)(a); i++)
#define vi vector<int>
#define f first
#define s second
#define all(v) (v).begin(), (v).end()
typedef long long ll;
const ll mod = 1e9 + 7;
const int N = 100005;
int id[N], low[N], timer;
vector<int> adj[N];
vector<int> x, y;
void dfs(int node, int parent = -1) {
id[node] = low[node] = ++timer;
bool multiple_edges = false;
for (int child : adj[node]) {
if (child == parent && !multiple_edges) {
multiple_edges = true;
continue;
}
if (!id[child]) {
dfs(child, node);
low[node] = min(low[node], low[child]);
} else {
low[node] = min(low[node], id[child]);
}
}
if (low[node] == id[node]) {
if(parent!=-1) {
x.push_back(node+1);
y.push_back(parent+1);
}
}
}
struct DSU {
vi e;
void init(int N) { e = vi(N,-1); }
int get(int x) { return e[x] < 0 ? x : e[x] = get(e[x]); }
bool sameSet(int a, int b) { return get(a) == get(b); }
int size(int x) { return -e[get(x)]; }
bool unite(int x, int y) {
x = get(x), y = get(y); if (x == y) return 0;
if (e[x] > e[y]) swap(x,y);
e[x] += e[y]; e[y] = x; return 1;
}
};
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
int n, m; cin >> n >> m;
DSU d1, d2;
d1.init(n);
d2.init(n);
F0R(_, m) {
int u, v; cin >> u >> v;
u--; v--;
if(d1.unite(u, v) || d2.unite(u, v)) {
adj[u].push_back(v);
adj[v].push_back(u);
}
}
F0R(i, n) if(!id[i]) dfs(i);
F0R(i, x.size()) cout << x[i] << " " << y[i] << "\n";
return 0;
}
