#include <iostream>
#include <cstdio>
#include <vector>
#define Nmax 100010
#define Mmax 500010
using namespace std;
vector <int> graf[Nmax];
int answer[Mmax];
int n,m,lim;

void ciclu_eulear(int i)
{
    while(!graf[i].empty())
    {
        int vecin = graf[i].back();
        graf[i].pop_back();
        vector<int> :: iterator it;
        for(it = graf[vecin].begin(); *it != i ; it++);
        graf[vecin].erase(it);
        ciclu_eulear(vecin);
    }
    answer[lim++] = i;
}

void read()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    scanf("%d %d",&n,&m);
    int x,y;
    for(int i = 0 ; i  < m ; i++)
    {
        scanf("%d %d",&x,&y);
        graf[x].push_back(y);
        graf[y].push_back(x);
    }
    for(int i =  1;  i <= n ; i++)
        if(graf[i].size() %2 == 1)
        {
            printf("-1");
            return;
        }
    ciclu_eulear(1);
    for(int i = 0 ; i < lim ; i++)
        printf("%d ",answer[i]);
}




int main()
{
    read();
    return 0;
}