#include <bits/stdc++.h>
#define x first
#define y second
using namespace std;
ifstream in("ciclueuler.in");
ofstream out("ciclueuler.out");
vector<pair<int,int>> v[100002];
int a[100002],viz[500002],k;
void dfs(int nr)
{
    for(;a[nr]<v[nr].size();a[nr]++)
        if(!viz[v[nr][a[nr]].y])
        {
            viz[v[nr][a[nr]].y]=1;
            dfs(v[nr][a[nr]].x);
        }
    if(k--)
        out<<nr<<" ";
}
int main()	
{
    int n,m,i,nr1,nr2;
    in>>n>>m;k=m;
    while(m--)
    {
        in>>nr1>>nr2;
        v[nr1].push_back({nr2,m});
        v[nr2].push_back({nr1,m});
        a[nr1]++;a[nr2]++;
    }
    for(i=1;i<=n;i++)
    {
        if(a[i]%2)
        {
            out<<-1;
            return 0;
        }
        a[i]=0;
    }
    dfs(1);
    return 0;
}