#include <stack>
#include <queue>
#include <vector>
#include <fstream>
#include <cstdlib>
#include <iterator>
#include <algorithm>

using namespace std;

const int N_MAX=100011;

stack<int> S;
vector<int> G[N_MAX], r;
vector<int>::const_iterator it, iend;

bool canHaveE(int N)
{
    int i, count;
    queue<int> Q;
    bool was[N_MAX]={false};

    for(i=1; i <= N; ++i)
        if(G[i].size()&1)
            return false;
    was[1]=true;
    for(Q.push(1), count=N-1; !Q.empty(); Q.pop())
    {
        i=Q.front();
        for(it=G[i].begin(), iend=G[i].end(); it < iend; ++it)
            if(false == was[*it])
            {
                --count;
                if(0 == count)
                    return true;
                was[*it]=true;
                Q.push(*it);
            }
    }
    return false;
}
void Euler(int x)
{
    int y;
    while(!G[x].empty())
    {
        y=G[x].back();
        G[x].pop_back();
        G[y].erase(find(G[y].begin(), G[y].end(), x));
        x=y;
        S.push(y);
    }
}
int main()
{
    int N, M, x, y;
    ifstream in("ciclueuler.in");
    ofstream out("ciclueuler.out");

    for(in>>N>>M; M; --M)
    {
        in>>x>>y;
        G[x].push_back(y);
        G[y].push_back(x);
    }
    if(!canHaveE(N))
    {
        out<<"-1\n";
        return EXIT_SUCCESS;
    }
    x=1;
    do {
          Euler(x);
          r.push_back(S.top()); S.pop();
       }while(!S.empty());
    copy(r.begin(), r.end(), ostream_iterator<int>(out, " "));
    out<<'\n';
    return EXIT_SUCCESS;
}