#include <fstream>
#include <vector>
#define NMAX 100001
#define MMAX 500001
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
struct muchie{int y,nr;};
int n,m;
bool sters[MMAX];
vector<muchie> G[NMAX];
vector<int> C;
void euler(int x);
int main()
{
    int i,x,y;
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>x>>y;
        G[x].push_back({y,i});
        G[y].push_back({x,i});
    }
    for(i=1;i<=n;i++)
        if(G[i].size()%2) {fout<<-1; return 0;}
    for(i=1;i<=n;i++)
        if(G[i].size())
        {
            euler(i);
            break;
        }
    if(C.size()!=m+1) {fout<<-1; return 0;}
    for(i=0;i<C.size();i++) fout<<C[i]<<' ';
    return 0;
}
void euler(int x)
{
    muchie m;
    while(!G[x].empty())
    {
        m=G[x].back(); G[x].pop_back();
        if(!sters[m.nr])
        {
            sters[m.nr]=1;
            euler(m.y);
        }
    }
    C.push_back(x);
}