#include <bits/stdc++.h>
#define SZ(x) ((int) (x).size())
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
const int NMAX=100005, MMAX=500005;
vector<int> G[NMAX];
bool usedEdge[MMAX];
int from[MMAX],to[MMAX];
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int n,m;
    fin>>n>>m;
    for(int i=0;i<m;i++)
    {
        int x,y;
        fin>>x>>y;
        G[x].push_back(i);
        G[y].push_back(i);
        from[i]=x;
        to[i]=y;
    }
    for(int i=1;i<=n;i++)
        if(SZ(G[i])&1)
        {
            fout<<-1;
            return 0;
        }
    vector<int> ans;
    vector<int> stk;
    stk.push_back(1);
    while(!stk.empty())
    {
        int node=stk.back();
        if(!G[node].empty())
        {
            int e=G[node].back();
            G[node].pop_back();
            if(!usedEdge[e])
            {
                usedEdge[e]=true;
                int tto=from[e]^to[e]^node;
                stk.push_back(tto);
            }
        }
        else
        {
            stk.pop_back();
            ans.push_back(node);
        }
    }
    for(int i=0;i<SZ(ans)-1;i++)
        fout<<ans[i]<<" ";
    return 0;
}