#include<cstdio>
#include<vector>
#include<stack>
#include<bitset>
using namespace std;
#define NMAX 100005
#define MMAX 500005
vector < pair <int,int> > v[NMAX];
vector < pair <int,int> >::reverse_iterator it;
stack <int> st;
bitset <MMAX> viz;
bitset <NMAX> L;
int n,m,x,y,z,ok,start,D[NMAX];
void dfs(int s)
{
    int i;
    L[s]=1;
    for (i=0;i<v[s].size();++i)
        if (!L[v[s][i].first])
            dfs(v[s][i].first);
}
int main()
{
    int i;
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    scanf("%d%d",&n,&m);
    for (i=1;i<=m;++i)
    {
        scanf("%d%d",&x,&y);
        v[x].push_back(make_pair(y,i));
        v[y].push_back(make_pair(x,i));
        ++D[x], ++D[y];
    }
    for (i=1;i<=n;++i)
        if (D[i])
        {
            start=i;
            dfs(i);
            break;
        }
    for (i=1;i<=n;++i)
        if ((D[i] && !L[i]) || D[i]%2)
        {
            printf("-1\n");
            return 0;
        }
    ok=1;
    st.push(start);
    while (!st.empty())
    {
        x=st.top();
        while (!v[x].empty())
        {
            it=v[x].rbegin();
            y=it->first, z=it->second;
            if (viz[z])
                v[x].pop_back();
            else
                break;
        }
        if (v[x].empty())
        {
            if (!ok)
                printf("%d ",x);
            ok=0;
            st.pop();
            continue;
        }
        viz[z]=1;
        st.push(y);
    }
    printf("\n");
    return 0;
}