#include <bits/stdc++.h>
#define fi first
#define se second
#define pii std::pair<int, int>
#define pb push_back
#define mk std::make_pair

using u64 = unsigned long long;
using u32 = unsigned int;
using i64 = long long;
const i64 iinf = 0x3f3f3f3f, linf = 0x3f3f3f3f3f3f3f3f;
const int N = 5e5 + 10;
int n, m, tot;
int h[N], cnt = 1;
struct node {
    int frm, to, nxt;
} e[N << 1];
int low[N], dfn[N], cut[N];
std::map<pii, int> mp;
void add(int u, int v) {
    e[++cnt].frm = u;
    e[cnt].to = v;
    e[cnt].nxt = h[u];
    h[u] = cnt;
}
void tarjan(int u, int fa) {
    dfn[u] = low[u] = ++tot;
    for(int i = h[u]; i; i = e[i].nxt) {
        int v = e[i].to;
        if(!dfn[v]) {
            tarjan(v, i);
            if(low[v] > dfn[u]) cut[i] = 1;
            low[u] = std::min(low[u], low[v]);
        } else if(i != (fa ^ 1)) {
            low[u] = std::min(low[u], dfn[v]);
        }
    }
}
int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);

    std::cin >> n >> m;

    for(int i = 1; i <= m; i++) {
        int u, v;
        std::cin >> u >> v;
        mp[mk(u, v)] = 1;
        if(u != v) add(u, v), add(v, u);
    }

    for(int i = 1; i <= n; i++) if(!dfn[i]) tarjan(i, -1);

    for(int i = 1; i <= cnt; i++) {
        if(cut[i]) {
            if(mp.count(mk(e[i].frm, e[i].to))) std::cout << e[i].frm << " " << e[i].to << "\n";
            else std::cout << e[i].to << " " << e[i].frm << "\n";
        }
    }

    return 0;
}