#include<bits/stdc++.h>
using namespace std;
#define rd(i,n) for(int i=0;i<n;i++)
#define rp(i,n) for(int i=1;i<=n;i++)
#define rep(i,a,b) for(int i=a;i<=b;i++)
#define per(i,a,b) for(int i=b;i>=a;i--)
#define st string
#define vt vector
#define pb push_back
//#define int long long
typedef long long ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
const int N=500005;
int n,m,a[N],b[N],c;
int dfn[N],low[N],ti;
vt<pii>G[N];
vt<int>ans;
inline void dfs(int x,int p){
    dfn[x]=low[x]=++ti;
    for(auto i:G[x])if(i.second!=p){
        if(!dfn[i.first]){
            dfs(i.first,i.second);
            low[x]=min(low[x],low[i.first]);
            if(dfn[i.first]==low[i.first]){
                ans.pb(i.second);
            }
        }else{
            low[x]=min(low[x],dfn[i.first]);
        }
    }
}
signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin>>n>>m;
    rp(i,m){
        cin>>a[i]>>b[i];
        G[a[i]].pb({b[i],i});
        G[b[i]].pb({a[i],i});
    }
    dfs(1,0);
    for(auto i:ans){
        cout<<a[i]<<" "<<b[i]<<endl;
    }

    return 0;
}
//Rain Rain Rain