/*
灏忓簾鐗╋紝杩欓兘涓嶄細 /cf
*/
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define mp make_pair
#define inf (ll)1e9
#define pii pair <ll, ll>
#define fr first
#define se second
const ll mod = 1e9 + 7;
char buf[1 << 21], *p1 = buf, *p2 = buf;
#define getchar() (p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, 1 << 18, stdin), p1 == p2) ? EOF : *p1++)
inline ll read() {
	ll x = 0, f = 1;
	char ch = getchar();
	while(ch < '0' || ch > '9') f = ((ch == '-') ? -1 : f), ch = getchar();
	while(ch >= '0' && ch <= '9') x = x * 10 + ch - '0', ch = getchar();
	return x * f;
}
inline void write(ll x) {
	if(x < 0) x = -x, putchar('-');
	if(x >= 10) write(x / 10);
	putchar(x % 10 + '0');
}
inline ll quickmod(ll x, ll y) {
	ll Ans = 1;
	while(y) {
		if(y & 1) Ans = (1ll * Ans * x) % mod;
		x = (1ll * x * x) % mod;
		y >>= 1;
	}
	return Ans;
}
inline void Add(ll &x, ll y) {
	x += y;
	if(x >= mod) x -= mod;
}
inline void Dec(ll &x, ll y) {
	x -= y;
	if(x < 0) x += mod;
}
inline ll add(ll x, ll y) {
	x += y;
	if(x >= mod) x -= mod;
	return x;
}
inline ll dec(ll x, ll y) {
	x -= y;
	if(x < 0) x += mod;
	return x;
}
struct UnionSet {
	ll fa[200005];
	inline void makeSet(ll x) {
		for(ll i = 1; i <= x; i++) fa[i] = i;
	}
	inline ll findSet(ll x) {
		if(x == fa[x]) return x;
		return fa[x] = findSet(fa[x]);
	}
	inline void unionSet(ll x, ll y) {
		x = findSet(x), y = findSet(y);
		if(x == y) return ;
		fa[x] = y;
	}
}P;
ll n, m;
struct st {
	ll v, id;
	st() {}
	st(ll A, ll B) {
		v = A, id = B;
	}
};
vector <st> G[100005];
ll U[500005], V[500005], vis[500005];

ll dfn[100005], low[100005], tot;
inline void Tarjan(ll x, ll fa) {
	dfn[x] = low[x] = ++tot;
	for(auto y : G[x]) {
		if(y.id == fa) continue;
		if(!dfn[y.v]) {
			Tarjan(y.v, y.id);
			if(low[y.v] > dfn[x]) vis[y.id] = 1;
			low[x] = min(low[x], low[y.v]);
		}
		else low[x] = min(low[x], dfn[y.v]);
	}
}
int main() {
//	freopen(".in", "r", stdin);
//	freopen(".out", "w", stdout);
	n = read(), m = read();
	P.makeSet(n);
	for(ll i = 1; i <= m; i++) {
		ll u = read(), v = read();
		U[i] = u, V[i] = v;
		G[u].push_back(st(v, i));
		G[v].push_back(st(u, i));
		P.unionSet(u, v);
	}
	for(ll i = 1; i <= n; i++) {
		if(P.findSet(i) != P.findSet(1)) {
			for(ll j = 1; j <= m; j++) vis[j] = 1;
			break;
		}
	}
	Tarjan(1, 0);
	for(ll i = 1; i <= m; i++) if(vis[i]) write(U[i]), putchar(' '), write(V[i]), putchar('\n');
	return 0;
}
/*
*/