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

typedef long long ll;
const int N=1e6+3;
int n,m,tim,f[N],dfn[N],low[N],kx[N],ky[N];
map<pair<int,int>,int>mp;
bool vis[N];
vector<int>ve[N]; 
int F(int x){return f[x]==x?x:f[x]=F(f[x]);}
void Dfs(int x,int fa)
{
	low[x]=dfn[x]=++tim;
	for(int y:ve[x])
	{
		if(y==fa){fa=0;continue;}
		if(dfn[y]){low[x]=min(low[x],dfn[y]);continue;}
		Dfs(y,x);low[x]=min(low[x],low[y]);
		if(low[y]>dfn[x])vis[mp[make_pair(x,y)]]=1;
	}
}
int main()
{
	cin>>n>>m;
	for(int i=1,x,y;i<=m;i++)
	{
	    cin>>x>>y;
		if(x==y)continue;
		ve[x].push_back(y),ve[y].push_back(x);
		mp[make_pair(x,y)]=i,kx[i]=x,ky[i]=y;
	}
	for(int i=1;i<=n;i++)if(!dfn[i])Dfs(i,0);
	for(int i=1;i<=m;i++)if(vis[i])cout<<kx[i]<<" "<<ky[i]<<endl;
}