#include <cstdio>
#define N 100002
#include <vector>

using namespace std;
FILE *f,*g;

struct bla
{
    int ve,m;
};
bool vizm[N];
vector <bla>graph[N];
int sortat[N],ss=0;

void topo(int nod)
{
    for(int i=0;i<graph[nod].size();++i)
        if(!vizm[graph[nod][i].m])
            vizm[graph[nod][i].m]=1,topo(graph[nod][i].ve);
    sortat[++ss]=nod;
}
int main()
{
    f=fopen("ciclueuler.in","r");
    g=fopen("ciclueuler.out","w");
    int n,m;
    fscanf(f,"%d %d",&n,&m);
    int x,y;
    for(int i=1;i<=m;++i)
    {
        fscanf(f,"%d %d",&x,&y);
        graph[x].push_back({y,i});
        graph[y].push_back({x,i});
    }
    for(int i=1;i<=n;++i)
        if(graph[i].size()%2!=0)
        {
            fprintf(g,"-1\n");
            return 0;
        }
    topo(1);
    for(int i=ss;i>1;--i)
        fprintf(g,"%d ",sortat[i]);
    fclose(f);
    fclose(g);
    return 0;
}