#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

const int nmax = 100000;
int n,m;
int gr[nmax + 5];
vector <pair<int,int>> v[nmax + 5];
bool f[nmax* 5 + 5];
vector <int> stk;

int main(){

    fin>>n>>m;
    stk.reserve(n);
    for(int i=1;i<=m;i++)
    {
        int x,y;
        fin>>x>>y;
        v[x].push_back({y,i});
        v[y].push_back({x,i});
        gr[x]++;
        gr[y]++;
    }
    for(int i=1;i<=n;i++)
        if(gr[i]%2==1)
        {
            fout<<-1;
            return 0;
        }
    stk.push_back(1);

    vector <int> sol;

    while(!stk.empty())
    {
        int top = stk.back();
        while(v[top].empty()==false && f[v[top].back().second])
            v[top].pop_back();

        if(v[top].empty()){
            stk.pop_back();
            sol.push_back(top);
            continue;
        }
        else
        {
            stk.push_back(v[top].back().first);
            f[v[top].back().second]=true;
        }
    }
    for(int i = 0 ; i< sol.size()-1;i++)
        fout<<sol[i]<<' ';


}