#include <fstream>
#include <vector>
#include <bitset>

using namespace std;

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

const int N = 1e5 + 2;
const int M = 5e5 + 2;

struct muchie {
    int x, y;
};

muchie e[M];
int n, m , prim[N];
bitset <M> sterse;
vector <int> vec[N];
vector <int> ras;

bool grd_pare(){
    for(int i=1; i<=n; i++){
        if(vec[i].size() % 2 != 0){
            return false;
        }
    }
    return true;
}

int celalalt_vf(muchie e, int x)
{
    return (e.x + e.y - x);
}

void euler(int x){
    while( prim[x] < (int)vec[x].size() ){
        int iec= vec[x][prim[x]++];
        muchie ec= e[iec];
        int y= celalalt_vf(ec, x);
        if( !sterse[iec] ){
            sterse[iec] = 1;
            euler(y);
        }
    }
    ras.push_back(x);
}

int main()
{
    in >> n >> m;
    for(int i=1; i<=m; i++){
        in >> e[i].x >> e[i].y;
        vec[e[i].x].push_back(i);
        vec[e[i].y].push_back(i);
    }

    if( !grd_pare() ){
        out << -1;
        return 0;
    }

    euler(1);

    if( (int)ras.size() != m + 1 ){
        out << -1;
        return 0;
    }

    for(auto i : ras){
        out << i << " ";
    }

    return 0;
}