#include <iostream>
#include <cstdio>
#include <vector>
#include <stack>
#define nmax 100002
using namespace std;

int n,m,viz[nmax],grad[nmax];
vector < int > graf[nmax],sol;
stack<int > st;

void citire()
{
    scanf("%d%d",&n,&m);
    for (int i=1; i<=m; ++i)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        graf[x].push_back(y);
        graf[y].push_back(x);
        grad[x]++;
        grad[y]++;
    }
}
void dfs(int nod)
{
    viz[nod]=1;
    for (vector < int > :: iterator it = graf[nod].begin(); it!=graf[nod].end(); ++it)
        if (!viz[*it])
            dfs(*it);
}

void parcurg (int v)
{
    while(1)
    {
        if (!graf[v].size())
            break;
        int w=graf[v].front();
        for (vector < int > :: iterator it = graf[w].begin();it!=graf[w].end();++it)
            if (*it==v)
                {
                    graf[w].erase(it);
                    break;
                }
        graf[v].erase(graf[v].begin());
        st.push(v);
        v=w;
    }
}
int solve()
{
    dfs(1);
    for (int i=1; i<=n; ++i)
        if (!viz[i])
            return 0;
    for (int i=1; i<=n; ++i)
        if (grad[i]%2!=0)
            return 0;
    int v=1;
    do
    {
        parcurg(v);
        v=st.top();
        st.pop();
        sol.push_back(v);
    }while (!st.empty());
    return 1;
}
int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    citire();
    int solutie=solve();
    if (solutie)
    {
        for (vector < int > :: iterator it = sol.begin();it!=sol.end();++it)
            printf("%d ",*it);
    }
    else
        printf("-1");
    return 0;
}