#include<cstdio>
using namespace std;

const int nMax = 100000, mMax = 500000;
int muchie[mMax * 2 + 1], nodV[mMax * 2 + 1], urm[mMax * 2 + 1], lst[nMax + 1], sol[mMax + 1];
bool viz[nMax], ut[mMax + 1], grad[nMax + 1];
int st[mMax + 1];
int nr = 0, nrS = 0, vf = 0;

FILE *in, *out;

inline void adauga(int i, int x, int y){
    nodV[++nr] = y;
    urm[nr] = lst[x];
    lst[x] = nr;
    muchie[nr] = i;
}

void dfs(){

    int nod, pos, vec, posp;
    while(vf){
        nod = st[vf - 1];
        pos = lst[nod];
        viz[nod] = true;
        vec = 0;

        if(lst[nod]){
            while(pos && !vec){
                if(!ut[muchie[pos]]){
                    ut[muchie[pos]] = true;
                    vec = nodV[pos];
                }

                //sterge
                if(ut[muchie[pos]]){
                    if(pos == lst[nod]){
                        lst[nod] = urm[pos];
                    }else{
                        urm[posp] = urm[pos];
                    }
                }

                posp = pos;
                pos = urm[pos];
            }
            if(vec) st[vf++] = vec;
        }else{
             sol[++nrS] = nod;
             vf--;
        }
    }
}

int main (){
    in = fopen("ciclueuler.in","r");
    out = fopen("ciclueuler.out","w");

    int n, m; fscanf(in,"%d%d", &n, &m);
    for(int i = 1, x, y; i <= m ; ++i){
        fscanf(in,"%d%d", &x, &y);
        adauga(i, x, y);
        adauga(i, y, x);

        grad[x] = 1 - grad[x];
        grad[y] = 1 - grad[y];
    }

    st[vf++] = 1;
    dfs();

    for(int i = 1 ; i <= n ; ++i){
        if(!viz[i] || grad[i]){
            fprintf(out,"-1\n");
            return 0;
        }
    }


    for(int i = nrS ; i > 1 ; --i)
        fprintf(out,"%d ", sol[i]);
    fprintf(out,"\n");
    return 0;
}