#include<cstdio>
#include<fstream>
#include<vector>
#define maxn 100001
#define maxm 500001
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
vector<int> a[maxn],sol;
bool viz[maxm];
int n,m,i,x[maxm],y[maxm];
inline void Euler(int s)
{
    sol.push_back(s);
    for(vector<int>::iterator it=a[s].begin();it!=a[s].end();it++)
        if(viz[*it]==0)
        {
            viz[*it]=1;
            Euler(x[*it]+y[*it]-s);
        }
}
int main()
{
    int i;
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>x[i]>>y[i];
        a[x[i]].push_back(i);
        a[y[i]].push_back(i);
    }
    for(i=1;i<=n;i++)
        if(a[i].size()&1)
           {
               fout<<"-1\n";
               fin.close();
               fout.close();
               return 0;
           }

    Euler(1);
    for(vector<int> :: iterator it=sol.end()-1;it!=sol.begin();--it)
        fout<<*it<<" ";
    fin.close();
    fout.close();
    return 0;
}