#include <cstdio>
#include <iostream>
#include <vector>
#include <queue>
#include <stack>

using namespace std;

FILE *in,*out;

const int nmax = 100000;
const int mmax = 500000;

struct Edge
{
    int from;
    int to;
    bool del;

};

Edge e[1 + mmax];

vector <int> g[1 + nmax]; //g[i][0] = indicele unei muchii incidente in nodul i
int n, m, nc;
int cc[1 + nmax];

void bfs(int start)
{
    queue <int> q;
    q.push(start);
    while(0 < q.size())
    {
        int from = q.front();
        q.pop();
        for(int i = 0; i < g[from].size(); i++)
        {
            int pedge = g[from][i];
            int to = e[pedge].to;
            if(to == from)
                to = e[pedge].from;
            if(cc[to] == 0)
            {
                cc[to] = nc;
                q.push(to);
            }
        }
    }
}

stack<int> st1, st2;

void euler(int from)
{
    if(0 < g[from].size())
    {
        int pedge = g[from].back(); //imi returneaza ultimul element din vector
        g[from].pop_back();
        if(e[pedge].del == 0)
        {
            int to = e[pedge].to;
            if(to == from)
                to = e[pedge].from;
            e[pedge].del = 1;
            st1.push(to);
            euler(to);
        }
        euler(from);
    } else {
      st2.push(from);
    }
}

int main()
{
    int start;

    in = fopen("ciclueuler.in","r");
    out = fopen("ciclueuler.out","w");

    fscanf(in, "%d %d", &n, &m);
    for(int i = 1; i <= m; i ++)
    {
        fscanf(in,"%d %d", &e[i].from, &e[i].to);
        e[i].del = 0;
        g[e[i].from].push_back(i);
        g[e[i].to].push_back(i);
    }

    bool flag = 0; //verifica paritatea gradelor
    for(int i = 1; i <= n; i++)
    {
        if(0 < g[i].size() && cc[i] == 0)
        {
            start = i;
            nc++;
            cc[i] = nc;
            bfs(i);
        }
        if(g[i].size() % 2 == 1)
            flag = 1;
    }

    if(nc <= 1 && flag == 0)
    {
        for(int i=1; i<=n; i++) {
          //cout<<i<<" -> ";
          for(int j=0; j<g[i].size(); j++) {
            int pedge = g[i][j];
            int to = e[pedge].to;
            if(to == i)
              to = e[pedge].from;
            //cout<<to<<" ";
          }
          //cout<<endl;
        }
        //cout<<endl;
        st1.push(start);
        euler(start);
        while(st2.size() > 0)
        {
            fprintf(out,"%d ",st2.top());
            st2.pop();
        }
    }
    else
    {
        fprintf(out, "-1");
    }
    return 0;
}