#include <fstream>
#include <vector>
#include <algorithm>
#include <stack>
using namespace std;
int n, m, a, b, i, j, gr[100001], k1, k2, nod;
bool viz[100001];
int c[500001], ce[500001];
vector <int> g[100001];
ifstream fin ("ciclueuler.in");
ofstream fout ("ciclueuler.out");

int main () {
    fin>>n>>m;
    for (i=1;i<=m;i++) {
        fin>>a>>b;
        gr[a]++; gr[b]++;
        g[a].push_back(b);
        g[b].push_back(a);
    }
    for (i=1;i<=n;i++)  {
        if (gr[i]%2!=0) {
            fout<<-1;
            return 0;
        }
    }
    for (i=1;i<=n;i++) {
        if (gr[i]>0) {
            c[++k1]=i;
            break;
        }
    }

    while (k1>0) {
        if (gr[c[k1]]>0)
        {
            int x=c[k1];
            nod=g[x][gr[x]-1];
            gr[x]--;
            g[nod].erase(find(g[nod].begin(),g[nod].end(),x));
            gr[nod]--;
            c[++k1]=nod;
        }
        else
        {
            ce[++k2]=c[k1--];
        }
    }
    if (k2!=m+1) {
        fout<<-1;
        return 0;
    }
    for (i=1;i<k2;i++)
    {
        fout<<ce[i]<<" ";
    }

    return 0;
}