#include<cstdio>
#include<fstream>
#include<vector>
#define maxn 100001
#define maxm 500001
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
vector<int> a[maxn],sol;
bool viz[maxm];
int n,m,i,x[maxm],y[maxm];
inline void dfs(int s)
{
    for(vector<int> :: iterator it=a[s].begin();it!=a[s].end();++it)
        if(viz[*it]==0)
            viz[*it]=1,dfs(x[*it]+y[*it]-s);
        g<<s<<' ';
}
int main(void)
{
    f>>n>>m;
    for(i=1;i<=m;i++)
    {
        f>>x[i]>>y[i];
        a[x[i]].push_back(i);
        a[y[i]].push_back(i);
    }
    for(i=1;i<=n;i++)
        if(a[i].size() & 1)
        {
            g<<"-1";
            return 0;
        }
    dfs(1);
    return 0;
}