#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define mp make_pair
#define pb push_back
#define x first
#define y second
#define pii pair<int, int>
#define p3i pair<pii, int>
#define pll pair<ll, ll>
#define p3l pair<pll, ll>
#define lseg L, (L+R)/2, N*2+1
#define rseg (L+R)/2+1, R, N*2+2
#define ub upper_bound
#define lb lower_bound
#define pq priority_queue
#define MN 1000000007
#define fox(k, x) for (int k=0; k<x; ++k)
#define fox1(k, x) for (int k=1; k<=x; ++k)
#define foxr(k, x) for (int k=x-1; k>=0; --k)
#define fox1r(k, x) for (int k=x; k>0; --k)
#define ms multiset
#define flood(x) memset(x, 0x3f3f3f3f, sizeof x)
#define drain(x) memset(x, 0, sizeof x)
#define rng() (rand() >> 3)*rand()
int n, m, a, b, r[100005], p[100005], d[100005];
bool u[100005];
vector<int> v[100005], com[100005];
bool mrg(int A, int B){
A=r[A]; B=r[B];
if (A==B) return 0;
if (com[A].size()<com[B].size()) return mrg(B, A);
for (auto i:com[B]){
com[A].pb(i);
r[i]=A;
}
return 1;
}
void dfs(int N, int P){
p[N]=P;
if (P!=-1) d[N]=d[P]+1;
fox(l, v[N].size()){
if (v[N][l]==P) continue;
dfs(v[N][l], N);
}
}
void lca(int X, int Y){
X=r[X]; Y=r[Y];
if (p[X]!=-1 && r[p[X]]==Y || p[Y]!=-1 && r[p[Y]]==X) return;
while(X!=Y){
if (d[X]>d[Y]){
u[X]=1;
X=r[p[X]];
} else {
u[Y]=1;
Y=r[p[Y]];
}
}
}
int main(){
scanf("%i%i", &n, &m);
fox1(l, n){
r[l]=l;
com[l].clear(); com[l].pb(l);
}
fox(l, m){
scanf("%i%i", &a, &b);
if (mrg(a, b)){
v[a].pb(b);
v[b].pb(a);
}
}
fox1(l, n){
if (p[l]==0){
dfs(l, -1);
}
}
fox1(l, n){
r[l]=l;
com[l].clear(); com[l].pb(l);
}
rewind(stdin);
scanf("%i%i", &n, &m);
fox(l, m){
scanf("%i%i", &a, &b);
lca(a, b);
}
fox1(l, n){
if (!u[l] && p[l]!=-1){
printf("%i %i\n", l, p[l]);
}
}
return 0;
}
