#include <cstdio>
#include <vector>
#include <algorithm>
#include <stack>

using namespace std;

const int nmx = 100002;

int n,m;
int grad[nmx];
vector <int> g[nmx];
stack <int> st;

void citire()
{
    scanf("%d %d", &n, &m);
    for(int i = 1; i <= m; ++i)
    {
        int nod1,nod2;
        scanf("%d %d", &nod1, &nod2);
        g[nod1].push_back(nod2);
        g[nod2].push_back(nod1);
        ++grad[nod2];
        ++grad[nod1];
    }
}

bool imparitate()
{
    for(int i = 1; i <= n; ++i)
        if(grad[i] % 2)
            return true;
    return false;
}

void rezolvare()
{
    st.push(1);

    while(not st.empty())
    {
        int nod = st.top();

        if(g[nod].size())
        {
            int nod1 = g[nod].back();
            st.push(nod1);
            g[nod].pop_back();
            g[nod1].erase(find(g[nod1].begin(),g[nod1].end(),nod));
        }
        else
        {
            st.pop();
            printf("%d ", nod);
        }
    }
}

int main()
{
    freopen("ciclueuler.in", "r", stdin);
    freopen("ciclueuler.out", "w", stdout);
    citire();
    if(imparitate())
    {
        printf("-1\n");
        return 0;
    }
    rezolvare();
    return 0;
}