#include<bits/stdc++.h>
using namespace std;
#define fq(i,l,r) for(int i=(l);i<=(r);i++)
#define ffq(i,r,l) for(int i=(r);i>=(l);i--)
#define pii pair<int,int>
#define F first
#define S second
const int N=5e5+9;
int n,m,x,y,dfn[N],low[N],cnt,v[N];
struct A{int u,v;} e[N];
vector<pii> q[N];
void tarjan(int p,int wh){
    low[p]=dfn[p]=++cnt;
    for(auto u:q[p]) 
        if(!dfn[u.F]){
            tarjan(u.F,u.S),low[p]=min(low[p],low[u.F]);
            // if(low[u.F]>dfn[x]) v[wh]=1;
        }
        else if(u.S!=wh) low[p]=min(low[p],dfn[u.F]);
    if(dfn[p]<=low[p]) v[wh]=1;
}
int main(){
    cin>>n>>m;
    fq(i,1,m) cin>>x>>y,q[x].push_back({y,i}),q[y].push_back({x,i}),e[i]={x,y};
    fq(i,1,n) if(!dfn[i]) tarjan(i,-1);
    fq(i,1,m) if(v[i]) cout<<e[i].u<<" "<<e[i].v<<endl;
    return 0;
}