#include <bits/stdc++.h>

using namespace std;

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

stack<int>s;
list<int>l[100010];
list<int>r;
list<int>::iterator it;

int main()
{
    int n,m,i,x=1,y,ok,j;
    fscanf(f,"%d%d",&n,&m);
    for (i=1;i<=m;i++){
        fscanf(f,"%d%d",&x,&y);
        l[x].push_back(y);
        l[y].push_back(x);
    }
    ok=1;
    for (i=1;i<=n;i++)
        if (l[i].size()%2==1) {ok=0;break;}
    if (!ok) fprintf(g,"-1");
    else{

    s.push(1);
    while (!s.empty()){
        i=s.top();ok=l[i].size();
        if (!l[i].empty()){
            j=l[i].back();
            l[i].pop_back();
            for (it=l[j].begin();it!=l[j].end();it++)
            if (*it==i) {l[j].erase(it);break;}
            s.push(j);
        }
        else{
            r.push_back(i);
        s.pop();
        }
    }
    r.pop_back();
    for (it=r.begin();it!=r.end();it++)
        fprintf(g,"%d ",*it);
    }
    fclose(f);
    fclose(g);
    return 0;
}