#include<bits/stdc++.h>
using namespace std;

int n,m;
int nxt[1000005],to[1000005],head[100005],ecnt=1;
int U[500005],V[500005];
void adde(int x,int y){
	nxt[++ecnt]=head[x];
	to[ecnt]=y;
	head[x]=ecnt;
}

int dfn[100005],low[100005],del[100005],dcnt;

void dfs(int x,int j){
	dfn[x]=low[x]=++dcnt;
	for(int i=head[x];i;i=nxt[i]){
		int y=to[i];
		if(i>>1==j)continue;
		if(dfn[y]==0){
			dfs(y,i>>1);
			low[x]=min(low[x],low[y]);
			if(low[x]<low[y])
				del[i>>1]=1;
		}
		else low[x]=min(low[x],dfn[y]);
	}
}


int main(){
	scanf("%d %d",&n,&m);
	for(int i=1;i<=m;++i){
		scanf("%d %d",&U[i],&V[i]);
		adde(U[i],V[i]);
		adde(V[i],U[i]);
	}
	for(int i=1;i<=n;++i)
		if(dfn[i]==0)dfs(i,-1);
	for(int i=1;i<=m;++i){
		if(del[i])
			printf("%d %d\n",U[i],V[i]);
	}
}