#include <bits/stdc++.h>
#define ll long long
#define pir pair <ll, ll>
#define mkp make_pair
#define fi first
#define se second
#define pb push_back
using namespace std;
const ll maxn = 5e5 + 10;
ll n, m, x[maxn], y[maxn], ans[maxn], len;
struct edge { ll v, nxt, id; } e[maxn];
ll head[maxn], tot, dfn[maxn], low[maxn], ti;
void ins(ll u, ll v, ll i) {
	e[++tot] = (edge) {v, head[u], i};
	head[u] = tot;
}
void tarjan(ll u, ll p) {
	dfn[u] = low[u] = ++ti;
	for(ll i = head[u]; i; i = e[i].nxt) {
		ll v = e[i].v, id = e[i].id;
		if(id == p) continue;
		if(dfn[v]) low[u] = min(low[u], dfn[v]);
		else {
			tarjan(v, id);
			low[u] = min(low[u], low[v]);
			if(low[v] > dfn[u]) ans[++len] = id;
		}
	}
}
int main(){
	scanf("%lld%lld", &n, &m);
	for(ll i = 1; i <= m; i++) {
		scanf("%lld%lld", x + i, y + i);
		ins(x[i], y[i], i), ins(y[i], x[i], i);
	}
	for(ll i = 1; i <= n; i++)
		if(!dfn[i]) tarjan(i, 0);
	sort(ans + 1, ans + 1 + len);
	for(ll i = 1; i <= len; i++)
		printf("%lld %lld\n", x[ans[i]], y[ans[i]]);
	return 0;
}