#include<map>
#include<set>
#include<queue>
#include<deque>
#include<stack>
#include<ctime>
#include<cmath>
#include<cctype>
#include<bitset>
#include<vector>
#include<cstdio>
#include<random>
#include<climits>
#include<cstring>
#include<iostream>
#include<algorithm>
#define inf 0x3f3f3f3f
#define INF 1e9
#define LLINF 1e18
#define ll long long
#define ld long double
#define FILE1(x) freopen(x".in","r",stdin),freopen(x".out","w",stdout)
#define FILE2(x) freopen(x".in","r",stdin),freopen(x".ans","w",stdout)
#define FILE3(x) freopen(x".in","r",stdin)
#define Mod 998244353
#define N 100005
#define M 500005
using namespace std;
int read(){
	int x=0,f=1,ch=getchar();
	for(;!isdigit(ch);ch=getchar()) f=(ch=='-')?-1:1;
	for(;isdigit(ch);ch=getchar()) x=(x<<3)+(x<<1)+(ch^48);
	return x*f;
}
int add(int x,int y){return x+y>=Mod?x+y-Mod:x+y;}
int del(int x,int y){return add(x,Mod-y);}
int mul(int x,int y){return ((ll)x*y)%Mod;}
void Add(int &x,int y){x=add(x,y);}
void Del(int &x,int y){x=del(x,y);}
void Mul(int &x,int y){x=mul(x,y);}
int n,m,head[N],tot=1;
int dfn[N],low[N],idx;
bool cut[N];
struct edge{int x,y;}E[M];
struct Edge{int to,nxt,id;}e[M<<1];
void add_edge(int x,int y,int i){
	e[++tot].to=y;
	e[tot].id=i;
	e[tot].nxt=head[x];
	head[x]=tot;
}
void tarjan(int x,int pree){
	dfn[x]=low[x]=++idx;
	for(int i=head[x];i;i=e[i].nxt){
		if(i==(pree^1)) continue;
		int y=e[i].to;
		if(!dfn[y]){
			tarjan(y,i);
			low[x]=min(low[x],low[y]);
			if(low[y]>dfn[x]) cut[e[i].id]=true;
		}
		else low[x]=min(low[x],dfn[y]);
	}
}
int main(){
	n=read(),m=read();
	for(int i=1;i<=m;++i){
		int x=read(),y=read();
		add_edge(x,y,i);
		add_edge(y,x,i);
		E[i]=(edge){x,y};
	}
	for(int i=1;i<=n;++i) if(!dfn[i]) tarjan(i,0);
	for(int i=1;i<=m;++i) if(cut[i]) printf("%d %d\n",E[i].x,E[i].y);
	return 0;
}