#include "bits/stdc++.h"
#ifdef DEBUG
#include "PrettyDebug.hpp"
#else
#define debug(...) [](auto...){}(__VA_ARGS__)
#define debuga(...) [](auto...){}(__VA_ARGS__)
#endif
#define For(i,a,b) for(int i=a;i<=b;i++)
#define Rev(i,a,b) for(int i=a;i>=b;i--)
#define Fin(file) freopen(file,"r",stdin)
#define Fout(file) freopen(file,"w",stdout)
using namespace std; typedef long long ll;
constexpr int N=1e5+5;
int n,m,a[N],b[N],dfn[N],low[N],dfscnt; vector<pair<int,int>> to[N]; vector<int> ans;
void dfs(int u,int fr){
    dfn[u]=low[u]=++dfscnt;
    for(auto [v,e]:to[u]) if(e!=fr){
        if(!dfn[v]){
            dfs(v,e),low[u]=min(low[u],low[v]);
            if(low[v]>dfn[u]) ans.push_back(e);
        }
        else{
            low[u]=min(low[u],dfn[v]);
        }
    }
}
signed main(){
    atexit([](){cerr<<"Time = "<<clock()<<" ms"<<endl;});
    cin>>n>>m; For(i,1,m) { int x,y; cin>>x>>y; to[x].emplace_back(y,i); to[y].emplace_back(x,i); a[i]=x,b[i]=y; }
    For(i,1,n) if(!dfn[i]) dfs(i,0);
    sort(ans.begin(),ans.end()); for(int e:ans) cout<<a[e]<<' '<<b[e]<<'\n';
    return 0;
}

// START TYPING IF YOU DON'T KNOW WHAT TO DO
// STOP TYPING IF YOU DON'T KNOW WHAT YOU'RE DOING
// CONTINUE, NON-STOPPING, FOR CHARLIEVINNIE

// Started Coding On: November 17 Fri, 16 : 17 : 11