#include <bits/stdc++.h>
#define MAXN 200005
#define fsync ios::sync_with_stdio(false);cin.tie(nullptr),cout.tie(nullptr)
using namespace std;
using ll = long long;
int n,m;
int low[MAXN],dfn[MAXN],num;
int idx[MAXN];
bool cut[MAXN];
int tot=1;
struct node{
	int u,v,nxt;
}e[MAXN];
void add(int u,int v){
	e[++tot]={u,v,idx[u]};idx[u]=tot;
	e[++tot]={v,u,idx[v]};idx[v]=tot;
}
void dfs(int x,int pre){
	low[x]=dfn[x]=++num;
	for(int i=idx[x];i;i=e[i].nxt){
		int v=e[i].v;
		if(i==pre || (i^1)==pre)continue;
		if(dfn[v])low[x]=min(low[x],dfn[v]);
		else{
			dfs(v,i);
			if(low[v]>dfn[x])cut[i]=cut[i^1]=1;
			low[x]=min(low[x],low[v]);
		}
	}
}
int main(){
	fsync;
	cin>>n>>m;
	for(int i=1;i<=m;i++){
		int x,y;cin>>x>>y;add(x,y);
	}
	for(int i=1;i<=n;i++){
		if(!dfn[i])dfs(i,0);
	}
	for(int i=1;i<=m;i++){
		if(cut[i*2]){
			cout<<e[i*2].u<<" "<<e[i*2].v<<"\n";
		}
	}
	return 0;
}