#include <bits/stdc++.h>
using namespace std;
const int N=1e5+10;
int dfn[N],low[N],stk[N];
int tot,num,col,top,bel[N];
struct node{int u,v;}e[N];
vector<vector<pair<int,int>>> G;
void tarjan(int x, int frm){
	dfn[x]=low[x]=++tot;
	stk[++top]=x;
	for (auto [id,v]:G[x]){
		if (!dfn[v]) tarjan(v,id),low[x]=min(low[x],low[v]);
		else if (id!=frm) low[x]=min(low[x],dfn[v]);
	}if (dfn[x]==low[x]){
		int k;col++;
		do{
			k=stk[top--];bel[k]=col;
		}while (k!=x);
	}return;
}
int main(){
	ios::sync_with_stdio(0);
	cin.tie(nullptr);cout.tie(nullptr);
	int n,m;cin>>n>>m;G.resize(n+10);
	for (int i=1;i<=m;i++){
		cin>>e[i].u>>e[i].v;
		G[e[i].u].emplace_back(i,e[i].v);
		G[e[i].v].emplace_back(i,e[i].u);
	}for (int i=1;i<=n;i++){
		if (!dfn[i]) tarjan(i,0);
	}for (int i=1;i<=m;i++){
		if (bel[e[i].u]!=bel[e[i].v]){
			cout<<e[i].u<<' '<<e[i].v<<endl;
		}
	}return 0;
}