#include <bits/stdc++.h>
#define ll long long
#define MAX 100000
#define INF 1000000000000000
#define mod 998244353
using namespace std;
int up[MAX + 1][17], de[MAX + 1], ans[MAX + 1];
vector<vector<int>> v;
void dfs(int x, int p){
up[x][0] = p, de[x] = de[p] + 1;
for (int i = 1; i < 17; i++){
up[x][i] = up[up[x][i - 1]][i - 1];
}
for (auto el : v[x]){
if (el != p) dfs(el, x);
}
}
int p[MAX + 1];
int find(int x){
if (p[x] < 0) return x;
return p[x] = find(p[x]);
}
void merge(int a, int b){
a = find(a), b = find(b);
if (a == b) return;
if (p[a] > p[b]) swap(a, b);
p[a] += p[b];
p[b] = a;
}
int gs(int x){
return -p[find(x)];
}
int dist(int x, int k){
for (int i = 0; i < 17; i++){
int val = k & (1<<i);
if (val != 0) x = up[x][i];
}
return x;
}
int lca(int a, int b){
if (de[a] > de[b]) swap(a, b);
b = dist(b, de[b] - de[a]);
if (a == b) return a;
for (int i = 16; i >= 0; i--){
if (up[a][i] != up[b][i]){
a = up[a][i];
b = up[b][i];
}
}
return up[a][0];
}
void dfs2(int x, int p){
for (auto el : v[x]){
if (el != p){
dfs2(el, x);
ans[x] += ans[el];
}
}
if (ans[x] == 0 && p != 0) cout<<x<<" "<<p<<"\n";
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int n, m, a, b;
cin>>n>>m;
for (int i = 1; i <= n; i++) p[i] = -1, de[i] = 1;
v.assign(n + 1, vector<int>());
for (int i = 0; i < m; i++){
cin>>a>>b;
int ra = find(a), rb = find(b);
if (ra != rb){
v[a].push_back(b);
v[b].push_back(a);
if (p[ra] > p[rb]){
dfs(a, b);
}
else{
dfs(b, a);
}
merge(ra, rb);
}
else{
int lc = lca(a, b);
ans[a]++, ans[b]++, ans[lc] -= 2;
}
}
for (int i = 1; i <= n; i++) if (de[i] == 1) dfs2(i, 0);
}
