#include <bits/stdc++.h>

using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
const int N = 100010;
const int M = 500010;
vector<int> v[N];
queue<int> q;
bitset<N> viz;
int n,m,cnt,a[M],b[M],arb[M];
void sorteaza(vector<int>&);
void dfs(int);
int main()
{
    f>>n>>m;
    for(int i=1; i<=m; i++)
    {
        int x,y;
        f>>x>>y;
        a[i]=x;
        b[i]=y;
        v[x].push_back(i);
        v[y].push_back(i);
    }
    for(int i=1; i<=n; i++)
        if(v[i].size()%2)
        {
            g<<"-1\n";
            return 0;
        }
    dfs(1);
    if(cnt!=n)
    {
        g<<"-1\n";
        return 0;
    }
    for(int i=1;i<=n;i++)
        sorteaza(v[i]);
    int nod=1;
    while(1)
    {
        while(v[nod].size()&&arb[v[nod].back()]==2)v[nod].pop_back();
        if(!v[nod].size())break;
        g<<nod<<' ';
        int much=v[nod].back();cnt--;
        arb[much]=2;
        nod=a[much]+b[much]-nod;
    }
    return 0;
}
void sorteaza(vector<int> &V)
{
    if(!V.size())return;
    int st=0,dr=V.size()-1;
    while(st<dr)
    {
        if(arb[V[st]])st++;
        else if(!arb[V[dr]])dr--;
        else { swap(V[st],V[dr]);st++;dr--;}
    }
}
void dfs(int nod)
{
    viz[nod]=1;
    cnt++;
    for(auto much:v[nod])
    {
        int vec=a[much]+b[much]-nod;
        if(!viz[vec])
        {
            arb[much]=1;
            dfs(vec);
        }
    }
}