#include <iostream>
#include <vector>
#include <bitset>
#include <random>
#include <chrono>
using namespace std;
const int N = 100005;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
vector<pair<int, int>> nei[N];
long long num[N];
int seen[N], Par[N];
int root(int v){
return (Par[v] == 0 ? v : Par[v] = root(Par[v]));
}
void dfs(int u, int p){
seen[u] = 1;
for (auto [i, id] : nei[u]){
if (i == p)
continue;
dfs(i, u);
if (num[i] == 0)
cout<<i<<" "<<u<<'\n';
num[u] ^= num[i];
}
}
int main(){
ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
int n, m;
cin>>n>>m;
for (int i=1, a, b;i<=m;i++){
long long rnd = 1, mod = 1e9 + 7;
for (int j=1;j<=10;j++)
rnd = rnd % mod * rng();
cin>>a>>b;
if (root(a) == root(b)){
num[a] ^= rnd;
num[b] ^= rnd;
}
else{
Par[root(a)] = root(b);
nei[a].push_back({b, i});
nei[b].push_back({a, i});
}
}
for (int i=1;i<=n;i++){
if (seen[i] == 0)
dfs(i, 0);
}
}
