#include <fstream>
#include <iostream>
#include <vector>
#include <stack>

using namespace std;

ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");

int grad[100005],n,m,flag;
vector <int>graf[100005],s,af;
stack<int>rez;

struct muchii{
    int x,y;
    bool v;
}mu[500005];

int main()
{
    f>>n>>m;
    int x,y;
    for(int i=1;i<=m;i++)
    {
        f>>x>>y;
        graf[x].push_back(i);
        graf[y].push_back(i);
        mu[i]={x,y,0};
    }
    for(int i=1;i<=n;i++)
        if(graf[i].size()%2==1){
            flag=1;
            break;
        }
    if(flag==1)
        g<<"-1";
    else{
        rez.push(1);
        while(!rez.empty()){
            int nod=rez.top();
            if(!graf[nod].empty()){
                int muchie=graf[nod].back();
                graf[nod].pop_back();
                if(!mu[muchie].v)
                    mu[muchie].v=1,rez.push(nod==mu[muchie].x?mu[muchie].y:mu[muchie].x);
            }
            else {
                af.push_back(nod);
                rez.pop();
            }
        }
    }
    for(int i=0;i<af.size();i++)
        g<<af[i]<<" ";
}