#include<fstream>
#include<vector>
#include<deque>
#include<algorithm>
#define nx 100007
using namespace std;
int n,m,i,j,x,y,viz[nx],grad[nx];
vector<int>v[nx];
deque<int>d;

ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

void bfs()
{
    d.push_back(1);
    viz[1]=1;
    while(!d.empty())
    {
        x=d.front(),d.pop_front();
        for(j=0;j<v[x].size();j++)
        if(!viz[v[x][j]])viz[v[x][j]]=1,d.push_back(v[x][j]);
    }
}


int main()
{
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>x>>y;
        v[x].push_back(y);
        v[y].push_back(x);
        grad[x]++;
        grad[y]++;
    }

    bfs();
    for(i=1;i<=n;i++)
     if(grad[i]%2 || !viz[i])
    {
        fout<<"-1";
        return 0;
    }

    d.push_back(1);
    while(!d.empty())
    {
        x=d.back();
        if(v[x].size())
        {
            y=v[x].back();
            d.push_back(y);
            v[x].pop_back();
            v[y].erase(find(v[y].begin(),v[y].end(),x));
        }
        else fout<<x<<' ',d.pop_back();
    }
    return 0;
}