#include <iostream>
#include <cstdio>
#include <vector>
#include <unordered_set>
#include <stack>
#define NMAX 100010

using namespace std;

int n, m, sterse;
int nodviz[NMAX];
vector<int> sol;
stack<int> st;

//vector<int> v[NMAX];
unordered_multiset<int> v[NMAX];

void citire()
{
    scanf("%d %d", &n, &m);
    int t1, t2;
    for (int i = 1; i <= m; i++)
    {
        scanf("%d %d", &t1, &t2);
        v[t1].insert(t2);
        v[t2].insert(t1);
    }
}

void euler()
{
    for (int i = 1; i <= n; i++)
        if (v[i].size()%2)
    {
         printf("-1");
            return;
    }
    st.push(1);
    while (!st.empty())
    {
        int top = st.top();

        if (v[top].size() == 0)
        {
            sol.push_back(top);
            nodviz[top]++;
            st.pop();
            continue;
        }
        int next = *v[top].begin();
        v[top].erase(v[top].begin());
        sterse++;
        v[next].erase(v[next].find(top));
        st.push(next);
    }
    for (int i = 1; i <= n; i++)
        if (nodviz[i] == 0)
        {
            printf("-1");
            return;
        }
    if (sterse != m)
    {
        printf("-1");
        return ;
    }
    for (int i = sol.size()-1; i > 0; i--)
        printf("%d ", sol[i]);
}

int main()
{
    freopen("ciclueuler.in", "r", stdin);
    freopen("ciclueuler.out", "w", stdout);

    citire();
    euler();

    return 0;
}