#include <bits/stdc++.h>

using namespace std;

#ifdef LOCAL
auto debug(auto ...b){((cerr << b << ' ') , ...); cerr << '\n';}
#else
#define debug(...) 0717
#endif

using ll = long long;
using uint = unsigned;
using ull = unsigned long long;

const int INF = 0x3F3F3F3F;
const ll INFl = 0x3F3F3F3F3F3F3F3F;

#define all(x) x.begin(),x.end()
#define r_all(x) x.rbegin(),x.rend()

const int N = 1e5 + 5;
const int M = 5e5 + 5;

int n , m;

struct edge {
	int to , nxt;
}e[M << 1];
int head[N] , cnt = 1;
void adde(int u , int v){
	e[ ++ cnt] = {v , head[u]};
	head[u] = cnt;
	e[ ++ cnt] = {u , head[v]};
	head[v] = cnt;
}
#define out(u) for(int i = head[u]; i; i = e[i].nxt)

int dfn[N] , low[N] , idx;
vector<int> bri;
void tarjan(int u , int in_edge){
	dfn[u] = low[u] = ++ idx;
	out(u){
		int v = e[i].to;
		if(!dfn[v]) {
			tarjan(v , i);
			low[u] = min(low[u] , low[v]);
		}
		else if((i ^ 1) != in_edge){
			low[u] = min(low[u] , dfn[v]);
		}
	}
	if(low[u] == dfn[u]){
		bri.push_back(in_edge & (in_edge ^ 1));
	}
//	debug(u , dfn[u] , low[u]);
}

signed main() {
#ifdef LOCAL
#elif defined(ONLINE_JUDGE)
#else
#endif
	
	ios::sync_with_stdio(0); cin.tie(0);
	
	cin >> n >> m;
	for(int i = 1; i <= m; ++ i){
		int u , v; cin >> u >> v;
		if(u == v) continue;
		adde(u , v);
	}
	
	for(int i = 1; i <= n; ++ i){
		if(!dfn[i]) tarjan(i , 0);
	}
	
	for(auto i : bri){
		if(!i) continue;
		int v = e[i].to , u = e[i + 1].to;
		cout << u << " " << v << '\n';
	}
	
	return 0;
}