#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

const int N = 2e5 + 50;

int n, m, dfn[N], low[N], tot, ex[N], ey[N];
int bridge[N];
vector<pair<int, int>> G[N];

void tarjan(int x, int e) {
	dfn[x] = low[x] = ++tot;
	int cnt = 0;
	for (auto [y, i] : G[x]) {
		if (!dfn[y]) {
			tarjan(y, i);
			low[x] = min(low[x], low[y]);
			if (dfn[x] < low[y]) {
				bridge[i] = true;
			}
		}
		else if (e != i) low[x] = min(low[x], dfn[y]);
	}
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout.tie(nullptr);
	cin >> n >> m;
	for (int i = 1; i <= m; ++i) {
		int x, y;
		cin >> x >> y;
		G[x].emplace_back(y, i);
		G[y].emplace_back(x, i);
		ex[i] = x, ey[i] = y;
	}
	for (int i = 1; i <= n; ++i)
		if (!dfn[i])
			tarjan(i, i);
	for (int i = 1; i <= m; ++i) if (bridge[i])
		cout << ex[i] << ' ' << ey[i] << '\n';
	return 0;
}