#include <bits/stdc++.h>
#define Maxx 1000001
using namespace std;
struct node{
    int x, y ;
} ;

bool compare(node a, node b){
    if(a.x < a.y){
        return true ;
    }
    else if(a.x == b.x){
        if(a.y < b.y) {
            return true ;
        }
        else{
            return false ;
        }
    }
    else{
        return false ;
    }
}
node sample[Maxx] ;
vector <int> g[Maxx] ;
bool visited[Maxx] ;
int low[Maxx] , discover[Maxx] , timer = 1 , j = 0 ;
void dfs(int start , int parent){
    visited[start] = true ;
    low[start] = discover[start] = ++timer ;
    for(int a : g[start]){
    	if(a == parent) continue ;
    	if(visited[a]){
            low[start] = min(low[start] , discover[a]) ;
        }
        else{
            dfs(a , start) ;
            low[start] = min(low[start] , low[a]) ;
            if(low[a] > discover[start]){
                sample[j].x = min(a,start) ;
                sample[j++].y = max(a,start) ;
            }
        }
    }
}

int main() {
    int n , m ;
    cin >> n >> m ;
    while(m--){
        int u , v ;
        cin >> u >> v ;
            g[u].push_back(v) ;
            g[v].push_back(u) ;
    }
        for(int i = 0 ; i < n ; i++){
            visited[i] = false ;
            low[i] = -1 ;
            discover[i] = -1 ;
        }
        for(int i = 0 ; i < n ; i++){
            if(!visited[i])
                dfs(i , -1) ;
        }
        sort(sample , sample + j , compare) ;
        int i = 0 ;
        while(j--){
            cout << sample[i].x << " " <<sample[i++].y << "\n" ;
        }
        timer = 1 ;
    return 0 ;
}