#include <iostream>
#include <algorithm>
#include <cstdio>
#include <stack>
#include <queue>
#include <list>

#define N 100005

using namespace std;

list<int> g[N];
int n,m,v[N];

void read()
{
    int a,b;
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;++i)
    {
        scanf("%d%d",&a,&b);
        g[a].push_back(b);
        g[b].push_back(a);
    }
}

void bfs(int k)
{
    queue<int> q;
    v[k]=1;
    q.push(k);
    while(!q.empty())
    {
        k=q.front();
        q.pop();
        for(list<int>::iterator it=g[k].begin();it!=g[k].end();++it)
            if(!v[*it])
            {
                v[*it]=1;
                q.push(*it);
            }
    }
}

bool is_eulerian()
{
    bfs(1);
    for(int i=1;i<=n;++i)
        if(g[i].size()%2||!v[i])
            return 0;
    return 1;
}

void solve()
{
    if(!is_eulerian())
        printf("-1");
    else
    {
        stack<int> s;
        int k=1,kv;
        do
        {
            while(!g[k].empty())
            {
                kv=g[k].front();
                s.push(k);
                g[k].pop_front();
                for(list<int>::iterator it=g[kv].begin();it!=g[kv].end();++it)
                    if(*it==k)
                    {
                        g[kv].erase(it);
                        break;
                    }
                k=kv;
            }
            k=s.top();
            s.pop();
            printf("%d ",k);
        }
        while(!s.empty());
    }
}

int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    read();
    solve();
    printf("\n");
    return 0;
}