#include<bits/stdc++.h>
using namespace std;
#define fr(i,a,b) for(int i=a;i<=b;i++)
#define ull unsigned long long
#define ll long long
#define mod 998244353
#define N 100005
#define M 1000005
int n,m,uu[N],vv[N];
int edt=1,head[N],to[M],nx[M],ew[M];
int dfn[N],low[N],dc;
int tmp[M],tk;
void adde(int u,int v,int w){
	to[++edt]=v,nx[edt]=head[u],ew[edt]=w,head[u]=edt;
}
void tarjan(int u,int eds){
	dfn[u]=low[u]=++dc;
	for(int ed=head[u];ed;ed=nx[ed]){
		int v=to[ed];
		if((ed^eds)==1)continue; 
		if(!dfn[v]){
			tarjan(v,ed);
			low[u]=min(low[u],low[v]);
			if(low[v]>dfn[u])tmp[++tk]=ew[ed];
		}
		else low[u]=min(low[u],dfn[v]);
	}
}
int main(){
	scanf("%d%d",&n,&m);
	fr(i,1,m){
		scanf("%d%d",&uu[i],&vv[i]);
		adde(uu[i],vv[i],i);
		adde(vv[i],uu[i],i);
	}
	fr(i,1,n)if(!dfn[i])tarjan(i,0);
	sort(tmp+1,tmp+tk+1);
	fr(i,1,tk)printf("%d %d\n",uu[tmp[i]],vv[tmp[i]]);
	return 0;
}