#include <bits/stdc++.h>
#define PB push_back
#define EB emplace_back
using namespace std;
const int maxn = 100000;
vector<int> e;
vector<int> g[maxn + 5];
int dfn[maxn + 5], low[maxn + 5], stamp;
int A[2 * maxn + 5], B[2 * maxn + 5];
void tarjan(int u, int fa) {
	dfn[u] = low[u] = ++stamp;
	for (int eid : g[u])
		if (eid != fa) {
			int v = e[eid];
			if (!dfn[v]) {
				tarjan(v, eid ^ 1);
				low[u] = min(low[u], low[v]);
			} else low[u] = min(low[u], dfn[v]);
			if (low[v] > dfn[u]) A[eid] = u, B[eid] = v;
		}
}
int main() {
	int n, m;
	scanf("%d%d", &n, &m);
	for (int i = 1; i <= m; i++) {
		int u, v;
		scanf("%d%d", &u, &v);
		g[u].PB(e.size()), e.PB(v);
		g[v].PB(e.size()), e.PB(u);
	}
	for (int i = 1; i <= n; i++)
		if (!dfn[i]) tarjan(i, -1);
	for (int i = 0; i < 2 * m; i++)
		if (A[i]) printf("%d %d\n", A[i], B[i]);
}