// Sea, You & Me
#include<bits/stdc++.h>
#define LL long long
#define DB double
#define MOD 1000000007
#define ls(x) (x << 1)
#define rs(x) (x << 1 | 1)
#define lowbit(x) ((-x) & x)
#define MP make_pair
#define MT make_tuple
#define VI vector<int>
#define VL vector<LL>
#define VII VI::iterator
#define VLI VL::iterator
#define all(x) x.begin(), x.end()
#define EB emplace_back
#define PII pair<int, int>
#define PLI pair<LL, int>
#define SI set<int>
#define SII SI::iterator
#define fi first
#define se second
using namespace std;
template<typename T> void chkmn(T &a, const T b) { (a > b) && (a = b); }
template<typename T> void chkmx(T &a, const T b) { (a < b) && (a = b); }
void Inc(int &a, const int &b) { ((a += b) >= MOD) && (a -= MOD); }
void Dec(int &a, const int &b) { ((a -= b) < 0) && (a += MOD); }
void Mul(int &a, const int &b) { a = 1LL * a * b % MOD; }
void Sqr(int &a) { a = 1LL * a * a % MOD; }
int inc(const int &a, const int &b) { return (a + b >= MOD) ? a + b - MOD : a + b; }
int dec(const int &a, const int &b) { return (a - b < 0) ? a - b + MOD : a - b; }
int mul(const int &a, const int &b) { return 1LL * a * b % MOD; }
int sqr(const int &a) { return 1LL * a * a % MOD; }
int qwqmi(int x, int k = MOD - 2)
{
	int res = 1;
	while(k)
	{
		if(k & 1) Mul(res, x);
		k >>= 1, Sqr(x);
	}
	return res;
}
template<typename T> void read(T &x)
{
	x = 0;
	int f = 1;
	char ch = getchar();
	while(!isdigit(ch))
	{
		if(ch == '-')
			f = -1;
		ch = getchar();
	}
	while(isdigit(ch))
	{
		x = (x << 1) + (x << 3) + (ch ^ 48);
		ch = getchar();
	}
	x = x * f;
}
const int N = 1e5 + 5;
const int M = 5e5 + 5;
int n, m;
PII ed[N];
struct Lexington
{
	int e, ne;	
};
struct Noshiro
{
	int idx = 1, h[N];
	Lexington lxt[M << 1];
	void clear()
	{
		idx = 1;
		memset(h, 0, sizeof(h));
	}
	void add(int x, int y)
	{
		lxt[++idx] = (Lexington){y, h[x]};
		h[x] = idx;
	}
	void adds(int x, int y)
	{
		add(x, y), add(y, x);
	}
}nsr;
int low[N], dfn[N], timestamp;
bool bridge[M];
void tarjan(int u, int from)
{
	low[u] = dfn[u] = ++timestamp;	
	for(int i = nsr.h[u]; i; i = nsr.lxt[i].ne)
	{
		int v = nsr.lxt[i].e;
		if(!dfn[v])
		{
			tarjan(v, i);
			chkmn(low[u], low[v]);
			if(dfn[u] < low[v])
				bridge[i / 2] = 1;
		}
		else if(i != (from ^ 1))
			chkmn(low[u], dfn[v]); 
	}
}
int main()
{
	read(n), read(m);
	for(int i = 1; i <= m; ++i)
	{
		int x, y;
		read(x), read(y);
		nsr.adds(x, y);
		ed[i] = MP(x, y);
	}
	for(int i = 1; i <= n; ++i)
		if(!dfn[i]) tarjan(i, 0);
	for(int i = 1; i <= m; ++i)
		if(bridge[i]) printf("%d %d\n", ed[i].fi, ed[i].se);
	return 0;
}