#include <bits/stdc++.h>
using namespace std;
#define sz(a) (int)a.size()
#define pb push_back
const int mxN = (int)5e5+10;
int n, m, vis[mxN], vis1[mxN], nx[mxN];
vector<pair<int,int>> v, adj[mxN];
void dfs(int s){
if(vis[s]==1){
int p = s;
while(vis[p]) cout<<p<<" ", vis[p]=0, p = nx[p];
cout << "\n";
} int pos = sz(adj[s])-1;
while(pos>=0){
auto [u,e] = adj[s][pos--];
if(!vis1[e]) vis1[e]=vis[s]=1, nx[s]=u, dfs(u);
}
}
int32_t main(){
cin >> n >> m;
for(int i = 0; i < m; i++){
int a, b; cin >> a >> b;
adj[a].pb({b,i}); adj[b].pb({a,i});
}
dfs(1);
}
