#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 5;
vector<pair<int, int>> edge[maxn];
int gb[maxn], n, m, low[maxn], dfn[maxn], cnt;
map<pair<int, int>, int> os;
pair<int, int> pii[maxn];
void tarjan(int now, int fa)
{
    low[now] = dfn[now] = ++cnt;
    int sum = 0;
    for (auto i : edge[now])
        if (!dfn[i.first])
        {
            sum++;
            tarjan(i.first, now);
            low[now] = min(low[now], low[i.first]);
            if (dfn[now] < low[i.first]) gb[i.second] = 1;
        }
        else if (i.first != fa) low[now] = min(low[now], dfn[i.first]);
}
int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    cin >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        int u, v;
        cin >> u >> v;
        os[make_pair(u, v)]++;
        pii[i] = make_pair(u, v);
        edge[u].emplace_back(v, i);
        edge[v].emplace_back(u, i);
    }
    for (int i = 1; i <= n; i++)
        if (!dfn[i]) tarjan(i, 0);
    for (int i = 1; i <= m; i++) if (gb[i] && os[pii[i]] == 1) cout << pii[i].first << ' ' << pii[i].second << '\n';
    return 0;
}