#include <cstdio>
#include <vector>
#include <stack>
#include <algorithm>
using namespace std;
const int nmax=1e5+3;
bool viz[nmax],grad[nmax];
vector <int> v[nmax];
int n,m,a,b,k,nod;
stack <int> st;
void dfs(int nod)
{
    viz[nod]=1;
    for(int i=0;i<v[nod].size();++i)
    {
        if(!viz[v[nod][i]]) dfs(v[nod][i]);
    }
}
int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;++i)
    {
        scanf("%d%d",&a,&b);
        v[a].push_back(b);
        v[b].push_back(a);
        grad[a]^=1;
        grad[b]^=1;
    }
    dfs(1);
    for(int i=1;i<=n;++i)
    {
        if(!viz[i]||grad[i])
        {
            printf("-1");
            return 0;
        }
    }
    st.push(1);
    while(!st.empty())
    {
        k=st.top();
        if(v[k].size())
        {
            nod=v[k].back();
            v[k].pop_back();
            st.push(nod);
            v[nod].erase(find(v[nod].begin(),v[nod].end(),k));
        }
        else
        {
            printf("%d ",k);
            st.pop();
        }
    }
    return 0;
}