#include<bits/stdc++.h>
using namespace std;

FILE *f=fopen("ciclueuler.in","r");
FILE *g=fopen("ciclueuler.out","w");

vector <int> v[100001];
stack <int> stiv;
int n,m,x,y,ok=1;

void euler()
{
    stiv.push(1);
    while(stiv.size()>0)
    {
        x=stiv.top();
        if(v[x].size()>0)
        {
            int y=v[x][0];
            stiv.push(y);
            v[x].erase(v[x].begin());
            v[y].erase(find(v[y].begin(),v[y].end(),x));
        }
        else
            fprintf(g,"%d ",x),stiv.pop();
    }
}
int main ()
{
    fscanf(f,"%d%d",&n,&m);
    for(int i=1; i<=m; i++)
    {
        fscanf(f,"%d%d",&x,&y);
        v[x].push_back(y);
        v[y].push_back(x);
    }
    for(int i=1; i<=n && ok==1; i++)   if(v[i].size()%2!=0)   ok=0;

    if(ok)
        euler();
    else
        fprintf(g,"%d ",-1);

}