//Huyduocdithitp
#include<bits/stdc++.h>
typedef int ll;
#define endl '\n'
#define fi first
#define se second
#define pii pair<ll,ll>
#define N 100005
#define LOG 18
using namespace std;
const ll inf = 1e9;
bool ghuy4g;
ll n, m;
vector<pii> adj[N];
ll num[N], low[N], timeDfs;
void dfs(ll u, ll parent) {
//cout <<u << " | " << parent << endl;
num[u] = low[u] = ++ timeDfs;
for (auto v : adj[u]) {
if (v.se == parent) continue;
if (num[v.fi]) {
low[u] = min(low[u], num[v.fi]);
}
else {
dfs(v.fi, v.se);
low[u] = min(low[u], low[v.fi]);
if (low[v.fi] == num[v.fi]) {
cout << u << " " << v.fi << endl;
}
}
}
}
void solve() {
for (int i = 1; i <= n; i ++) {
if (num[i] == 0) {
dfs(i, 0);
}
}
}
bool klinh;
signed main() {
//freopen("test.inp", "r", stdin);
//freopen("test.out", "w", stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> m;
for (int i = 1; i <= m; i ++) {
ll u, v;
cin >> u >> v;
adj[u].push_back({v, i});
adj[v].push_back({u, i});
}
solve();
cerr << fabs(&klinh - &ghuy4g) / double(1024 * 1024);
return 0;
}
