#include<fstream>
#include<vector>
#include<algorithm>
#include<deque>
#define nx 100007
using namespace std;
int n,m,x,y,i,j,l,grad[nx],viz[nx];
vector<int>v[nx];
deque<int>q;

ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

void dfs(int x)
{
    viz[x]=1;
    for(int j=0;j<v[x].size();j++)if(!viz[v[x][j]])dfs(v[x][j]);
}

void euler(int x)
{
    while(v[x].size())
    {
        l=v[x].size();
        y=v[x][l-1];
        v[x].pop_back();
        v[y].erase(find(v[y].begin(),v[y].end(),x));
        euler(y);
    }
    q.push_back(x);
}

int main()
{
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>x>>y;
        v[x].push_back(y);
        v[y].push_back(x);
        grad[x]++;
        grad[y]++;
    }

    dfs(1);
    for(i=1;i<=n;i++)

    if(!viz[x] && grad[i]%2)
    {
        fout<<'-1';
        return 0;
    }

    euler(1);
    while(q.size()!=1)fout<<q.front()<<' ',q.pop_front();
    return 0;
}