# include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 5; 
vector <pair<int,int> > g[N];
pair<int,int> E[N * 5]; 
int n, m; 
int dfn[N], low[N], dfntot = 0; 
bool ok[N]; 
void tarjan(int x, int lst)
{
	dfn[x] = low[x] = ++dfntot; 
	for(auto I : g[x])
	{
		int v = I.first, id = I.second; 
		if(id == lst) continue; 
		if(!dfn[v]) tarjan(v, id), low[x] = min(low[x], low[v]);
		else low[x] = min(low[x], dfn[v]); 
		if(low[v] > dfn[x]) 
		{
			ok[id] = 1; 
		}
	}
}
int main(void)
{
	scanf("%d%d", &n, &m);
	for(int i = 1; i <= m; i++)
	{
		int u, v; scanf("%d%d", &u, &v); 
		g[u].push_back({v, i}), g[v].push_back({u, i}); 
		E[i] = {u, v};
	}
	for(int i = 1; i <= n; i++) if(!dfn[i]) tarjan(i, 0);
	for(int i = 1; i <= m; i++) 
	{
		if(ok[i]) printf("%d %d\n", E[i].first, E[i].second);
	}
	return 0; 
}