#include <bits/stdc++.h>
#define st first
#define nd second
#define pb push_back
using namespace std;
FILE *fin=fopen("ciclueuler.in","r");
FILE *fout=fopen("ciclueuler.out","w");
const int N=100001, M=500005;
bool used[M];
int n, m, i, j, x, y;
pair<int,int> edg[M];
multiset<int> v[N];
vector<int> ans;
void dfs(int nod)
{
    multiset<int>::iterator it, it2;
    for(it=v[nod].begin();it!=v[nod].end();)
    {
        if(used[*it])
        {
            it2=it;
            ++it2;
            v[nod].erase(it);
            it=it2;
        }
        else
        {
            int mc=*it;
            used[*it]=1;
            if(edg[*it].st==nod)
                dfs(edg[*it].nd);
            else dfs(edg[*it].st);
            ++it;
        }
    }
    ans.pb(nod);
}
void no()
{
    fprintf(fout,"-1\n");
    exit(0);
}
int main()
{
    fscanf(fin,"%d%d",&n,&m);
    for(i=1;i<=m;++i)
    {
        fscanf(fin,"%d%d",&x,&y);
        v[x].insert(i);
        v[y].insert(i);
        edg[i].st=x,edg[i].nd=y;
    }
    for(i=1;i<=n;++i)
        if(v[i].size()%2||v[i].empty())
            no();
    dfs(1);
    for(i=1;i<=m;++i)
        if(!used[i])
            no();
    for(auto i:ans)
        fprintf(fout,"%d ",i);
    return 0;
}