#include<stdio.h>
#include<vector>
#define Nmx 500005
#define pb push_back

using namespace std;

vector<int> C[Nmx];
int grd[Nmx],n,m,nr,s[Nmx];

void citire()
{
    int x,y;
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;++i)
    {
        scanf("%d%d",&x,&y);
        grd[x]++;
        grd[y]++;
        C[x].pb(y);
        C[y].pb(x);
    }
}

void solve()
{
    for(int i=1;i<=n;++i)
        if(grd[i]&1)
        {
            printf("-1\n");
            return;
        }
    s[++nr]=1;
    while(nr)
    {
        int nod=s[nr];
        if(!C[nod].empty())
        {
            int x=C[nod].back();
            C[nod].pop_back();
            vector<int> :: iterator it;
            for (it=C[x].begin() ; it!=C[x].end() && *it!=nod ;it++);
                C[x].erase(it);
            s[++nr]=x;
        }
        else printf("%d ",s[nr--]);
    }
}

int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    citire();
    solve();
}