#include <bits/stdc++.h>
using namespace std;
#define For(Ti,Ta,Tb) for(auto Ti=(Ta);Ti<=(Tb);++Ti)
#define Dec(Ti,Ta,Tb) for(auto Ti=(Ta);Ti>=(Tb);--Ti)
#define debug(...) fprintf(stderr,__VA_ARGS__)
#define range(Tx) begin(Tx),end(Tx)
using ll=long long;
const int N=1e5+5,M=5e5+5;
int n,m,dfn[N],low[N],dfx,cut[N];
vector<pair<int,int>> g[N];
struct Edge{
	int u,v;
}edge[M];
void tarjan(int u,int pre){
	dfn[u]=low[u]=++dfx;
	for(auto [v,i]:g[u]) if(i!=pre){
		if(!dfn[v]){
			tarjan(v,i);
			low[u]=min(low[u],low[v]);
		}else{
			low[u]=min(low[u],dfn[v]);
		}
		if(low[v]>dfn[u]) cut[i]=1;
	}
}
int main(){
	cin.tie(nullptr)->sync_with_stdio(false);
	cin>>n>>m;
	For(i,1,m){
		int u,v;
		cin>>u>>v;
		edge[i]={u,v};
		g[u].emplace_back(v,i);
		g[v].emplace_back(u,i);
	}
	For(i,1,n) if(!dfn[i]) tarjan(i,0);
	For(i,1,m) if(cut[i]) cout<<edge[i].u<<' '<<edge[i].v<<'\n';
	return 0;
}