#include <cstdio>
#include <vector>

using namespace std;

FILE *fin, *fout;

#define NMAX 100000
vector<int> graph[NMAX + 5];
int n;
bool euler()
{
    int i;
    for(i = 1; i <= n; i++)
    {
        if(graph[i].size() % 2 != 0)
            return false;
    }

    return true;
}

struct edge
{
    int start, finish;
};

vector <edge> edges;

#define MMAX 500000
bool viz[MMAX + 5];

int rez[MMAX + 5] , k;

void dfs(int node)
{
    for(int i = 0; i < graph[node].size(); i++)
    {
        int e = graph[node][i];

        if(viz[e] == 0)
        {
            viz[e] = 1;

            dfs(edges[e].start + edges[e].finish - node);
        }
    }

    rez[++k] = node;
}

int main()
{
    fin = fopen("ciclueuler.in", "r");
    fout = fopen("ciclueuler.out", "w");

    int m;
    fscanf(fin, "%d%d", &n, &m);

    int u, v, i;
    edges.reserve(m);

    for(i = 0; i < m; i++)
    {
        fscanf(fin, "%d%d", &u, &v);
        edge e;
        e.start = u;
        e.finish = v;
        edges.push_back(e);

        graph[u].push_back(i);
        graph[v].push_back(i);
    }

    /*for(i = 1; i <= n; i++)
    {
        fprintf(fout, "%d: ", i);
        for(auto it : graph[i])
        {
            fprintf(fout, "%d ", it);

        }
        fprintf(fout, "\n");
    }*/

    if(euler() == false)
        fprintf(fout, "-1");
    else
    {
        dfs(1);

        for(i = 2; i <= k; i++)
            fprintf(fout, "%d ", rez[i]);
    }

    fclose(fin);
    fclose(fout);
    return 0;
}