#include<bits/stdc++.h>
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
const int NMAX=100005,MMAX=500005;
int n,m;
bitset<MMAX>usedEdge;
vector<int>eulerian_cycle,graph[NMAX];
struct Edge
{
    int from,to;
}edges[MMAX];
bool is_eulerian()
{
    ///not correct, should also check connectivity
    ///check for even degrees
    for(int i=1;i<=n;i++)
        if(graph[i].size()%2)
            return 0;
    return 1;
}
void dfs_euler(int node)
{
    stack<int>s;
    s.push(node);
    while(!s.empty())
    {
        node=s.top();
        if(graph[node].size())
        {
            int edge_idx=graph[node].back();
            graph[node].pop_back();
            if(!usedEdge[edge_idx])
            {
                usedEdge[edge_idx]=1;
                dfs_euler(edges[edge_idx].from^edges[edge_idx].to^node);
            }
        }
        else
        {
            s.pop();
            eulerian_cycle.push_back(node);
        }
    }
}
int main()
{
    f>>n>>m;
    for(int i=1,x,y;i<=m;i++)
    {
        f>>x>>y;
        graph[x].push_back(i);
        graph[y].push_back(i);
        edges[i].from=x;
        edges[i].to=y;
    }
    if(is_eulerian())
    {
        dfs_euler(1);
        for(int i=0;i<(int)eulerian_cycle.size()-1;i++)
            g<<eulerian_cycle[i]<<' ';
    }
    else
        g<<-1;
    return 0;
}