#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 5, MAXM = 5e5 + 5;
int read(){
    int res = 0, flag = 1;
    char c = getchar();
    for (; c < '0' || c > '9'; c = getchar())
        if (c == '-')
            flag = -1;
    for (; c >= '0' && c <= '9'; c = getchar())
        res = (res << 1) + (res << 3) + (c ^ 48);
    return res * flag;
}
class Graph{
private:
    const static int MAXNODE = MAXN;
    const static int MAXEDGE = 2 * MAXM;
    struct Edge{
        int v, next;
    };
public:
    int tot = 1;
    int h[MAXNODE];
    Edge t[MAXEDGE]; 
    void addEdge(int u, int v){
        ++tot;
        t[tot].v = v;
        t[tot].next = h[u];
        h[u] = tot;
    }
}G;
int cnt = 0;
int dfn[MAXN], low[MAXN];
int cut[2 * MAXM];
void dfs(int u, int from){
    dfn[u] = low[u] = ++cnt;
    for (int i = G.h[u]; i; i = G.t[i].next){
        if ((i ^ 1) == from)
            continue;   
        int v = G.t[i].v;
        if (!dfn[v]){
            dfs(v, i);
            low[u] = min(low[u], low[v]);
        }else{
            low[u] = min(low[u], dfn[v]);
        }
        if (low[v] > low[u])
            cut[i] = 1;
    }
}
int main(){
    int n = read(), m = read();
    for (int i = 1; i <= m; i++){
        int u = read(), v = read();
        G.addEdge(u, v);
        G.addEdge(v, u);
    }
    for (int i = 1; i <= n; i++)
        if (!dfn[i])
            dfs(i, 0);
    for (int i = 2; i <= G.tot; i += 2){
        if (cut[i])
            cout << G.t[i ^ 1].v << ' ' << G.t[i].v << endl;
    }
    return 0;
}