#include <bits/stdc++.h>
#define il inline
#define pii pair<int,int>
#define fi first
#define se second
using namespace std;
const int N=1e5+5;
int n,m,dfn[N],low[N],cnt,vis[N];pii g[N*5];
int st[N],top,bel[N],idx;
vector<pii> e[N];
il void adde(int x,int y,int z){e[x].push_back({y,z});}
void tarjan(int x,int pre){
    int y,z;dfn[x]=low[x]=++cnt,st[++top]=x;
    for(auto it:e[x]){
        y=it.fi,z=it.se;if(z==pre) continue;
        if(!dfn[y]) tarjan(y,z),low[x]=min(low[x],low[y]);
        else low[x]=min(low[x],dfn[y]);
    }
    if(dfn[x]==low[x]){
        ++idx;
        do{
            y=st[top--],bel[y]=idx;
        }while(y!=x);
    }
}
int x,y;
int main(){
    //freopen("bridge.in","r",stdin);
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;++i){
        scanf("%d%d",&x,&y);if(x!=y) adde(x,y,i),adde(y,x,i);
        g[i]={x,y};
    }
    for(int i=1;i<=n;++i) if(!dfn[i]) tarjan(i,0),top=0;
    for(int i=1;i<=n;++i)
        for(auto it:e[i]) if(bel[i]!=bel[it.fi]) vis[it.se]=1;
    for(int i=1;i<=m;++i) if(vis[i]) printf("%d %d\n",g[i].fi,g[i].se);

    return 0;
}