#include <iostream>
#include<cstdio>
#include<vector>
using namespace std;
const int N=100001;
const int M=5*N;
FILE*fin,*fout;
struct ajutormuchii{
  int dest;
  int id;
};
bool vizm[M];
bool vizn[N+5];
vector<ajutormuchii> gr[N];
void dfs_euler(int nod,int &cntafis,int m){
  for(auto x:gr[nod]){
    if(vizm[x.id]==false){
      vizm[x.id]=true;
      dfs_euler(x.dest,cntafis,m);
    }
  }
  if(cntafis<m){
    fprintf(fout,"%d ",nod);
    cntafis++;
  }
}
int cnt=0;
void dfs_nod(int nod){
  cnt++;
  vizn[nod]=true;
  for(auto x:gr[nod]){
    if(!vizn[x.dest])
      dfs_nod(x.dest);
  }
}
int main()
{
  int n,m;
  fin=fopen("ciclueuler.in","r");
  fout=fopen("ciclueuler.out","w");
  fscanf(fin,"%d%d",&n,&m);
  int id=0;
  for(int i=1;i<=m;i++){
    int x,y;
    fscanf(fin,"%d%d",&x,&y);
    ++id;
    gr[x].push_back({y,id});
    gr[y].push_back({x,id});
  }
  cnt=0;
  dfs_nod(1);
  if(cnt!=n){
    fprintf(fout,"-1\n");
    return 0;
  }
  for(int i=1;i<=n;i++){
    if(gr[i].size()%2==1){
      fprintf(fout,"-1\n");
      return 0;
    }
  }
  int c=0;
  dfs_euler(1,c,m);
  return 0;
}