#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];
vector<int> ans, v[N];
stack<int> stk;
void euler(int nod)
{
    stk.push(nod);
    while(!stk.empty())
    {
        nod=stk.top();
        while(!v[nod].empty()&&used[v[nod].back()])
            v[nod].pop_back();
        if(!v[nod].empty())
        {
            int mc=v[nod].back();
            v[nod].pop_back();
            used[mc]=1;
            stk.push(edg[mc].st^edg[mc].nd^nod);
        }
        else
        {
            ans.pb(nod);
            stk.pop();
        }
    }
}
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].pb(i);
        v[y].pb(i);
        edg[i].st=x,edg[i].nd=y;
    }
    for(i=1;i<=n;++i)
        if(v[i].size()%2||v[i].empty())
            no();
    euler(1);
    for(i=1;i<=m;++i)
        if(!used[i])
            no();
    for(auto i:ans)
        fprintf(fout,"%d ",i);
    return 0;
}