#include<iostream>
#include<fstream>
#include<vector>
#include<list>
using namespace std;
ifstream f("ciclueuler.in");
ofstream o("ciclueuler.out");
int vf, x, y;
int v, n=0;
list<int>*Adj;
vector<int> cicle;

int euler(int s){
while(!Adj[s].empty()){
v=Adj[s].front();
Adj[s].pop_front();
euler(v);
}
cicle.push_back(s+1);
n++;
}

int main(){
f>>vf>>x;
Adj=new list<int>[vf];
while(f>>x){
f>>y;
Adj[x-1].push_back(y-1);
Adj[y-1].push_back(x-1);
}

euler(0);
for(int i=0;i<n;i++){
o<<cicle[i]<<" ";
}
if(n==0) o<<-1;
}