#include <bits/stdc++.h>

using namespace std;

vector <int> a[100005], ans;
stack <int> s;

int main()
{
    freopen("ciclueuler.in", "r", stdin);
    freopen("ciclueuler.out", "w", stdout);
    int n, m;
    scanf("%d%d", &n, &m);
    for(int i = 1; i <= m; ++i) {
        int x, y;
        scanf("%d%d", &x, &y);
        a[x].push_back(y);
        a[y].push_back(x);
    }
    for(int i = 1; i <= n; ++i) {
        if(a[i].size() % 2 || !a[i].size()) {
            printf("-1");
            return 0;
        }
    }
    s.push(1);
    while(!s.empty()) {
        int x = s.top();
        if(!a[x].empty()) {
                int v = *a[x].begin();
                vector <int>::iterator it = find(a[v].begin(), a[v].end(), x);
                a[v].erase(it);
                a[x].erase(a[x].begin());
                s.push(v);
        }
        else {
            s.pop();
            ans.push_back(x);
        }
    }
    ans.pop_back();
    for(auto v : ans) printf("%d ", v);
    return 0;
}