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

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

vector<int> L[100005];
int n , m , x[500005] , y[500005] , d[100005];
int e[600005] , len , viz[500005] , p[100005];

int GradePare()
{
    for(int i = 1;i <= n;i++)
        if(d[i] % 2 == 1) return 0;
    return 1;
}

void Euler(int k)
{
    while(p[k] < L[k].size())
    {
        int i = L[k][p[k]];
        p[k]++;
        if(viz[i] == 0)
        {
            viz[i] = 1;
            Euler(x[i] + y[i] - k);
        }
    }
    e[++len] = k;
}

int main()
{
    int i , j , k;
    fin >> n >> m;
    for(k = 1;k <= m;k++)
    {
        fin >> i >> j;
        d[i]++; d[j]++;
        L[i].push_back(k);
        L[j].push_back(k);
        x[k] = i; y[k] = j;
    }
    if(GradePare() == 0)
    {
        fout << "-1";
        return 0;
    }
    Euler(1);
    for(i = 1;i < len;i++)
        fout << e[i] << " ";
    return 0;
}