#include <bits/stdc++.h>

#define NMax 100002
//#define f cin
//#define g cout
using namespace std;

ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");

int n,m,x,y;
int grad[NMax];
vector<int> G[NMax];
stack<int> s;

void elimin_muchie(int u,int v){
    for(int i = 0; i < G[u].size(); ++i){
        if(G[u][i] == v){
            G[u].erase(G[u].begin() + i);
            return;
        }
    }
}
int main()
{
    f >> n >> m;
    for(int i = 1; i <= m; ++i){
        f >> x >> y;
        G[x].push_back(y);
        G[y].push_back(x);
        grad[x]++;
        grad[y]++;
    }
    s.push(1);

    for(int i = 1; i <= n; ++i){
        if(grad[i] % 2 == 1){
            g << -1 << '\n';
            return 0;
        }
    }

    int k = 0;

    while(!s.empty()){
        int nod = s.top();
        if(G[nod].size() == 0){
            s.pop();
            if(k < m)
                g << nod << ' ';
            ++k;
        }else{
            int v = G[nod][G[nod].size() - 1];
            G[nod].erase(G[nod].begin() + G[nod].size() - 1);
            elimin_muchie(v,nod);
            s.push(v);
        }
    }
    return 0;
}