#include<bits/stdc++.h>
using namespace std;
 // #define int long long
#define F(i, l, r) for(int i = (l); i <= (r); ++i)
#define dF(i, r, l) for(int i = (r); i >= (l); --i)

int ri() {
	int x = 0, f = 1;
	char c = getchar();
	while(c < '0' || c > '9') {
		if(c == '-') f = -1;
		c = getchar();
	}
	while(c >= '0' && c <= '9') {
		x = x* 10 + c - 48;
		c  = getchar();
	} return x * f;
}

const int _ = 5e5 + 5;

int tot = 1, head[_], to[_ << 1], nxt[_ << 1];

void add(int u, int v) {
	to[++tot] = v, nxt[tot] = head[u], head[u] = tot;
}

int dfn[_], low[_], cnt;

struct node {
	pair<int, int> a;
	int Id;
};
map<pair<int, int>, node > mp;

vector<node> ans;

void tarjan(int u, int Id = 0) {
	dfn[u] = low[u] = ++cnt;
	for(int i = head[u], v = to[i]; i; i = nxt[i], v = to[i]) {
		if(!dfn[v]) {
			tarjan(v, i);
			 low[u] = min(low[u], low[v]);
			 if(low[v] > low[u]) {
			 	ans.push_back(mp[{u, v}]);
			 }
		} else if(i != (Id ^ 1)) {
			low[u] = min(low[u], dfn[v]);
		}
	}
}
signed main() {
	int n = ri(), m = ri();
	F(i, 1, m) {
		int u = ri(), v = ri();
		add(u, v), add(v, u);
		mp[{u, v}] = mp[{v, u}] = (node){make_pair(u, v), i};
	}
	F(i, 1, n) if(!dfn[i]) tarjan(i);
	sort(ans.begin(), ans.end(), [&](node a, node b) { return a.Id < b.Id;});
	for(node v : ans) {
		cout << v.a.first << ' ' << v.a.second << '\n';
	}
}