#include <iostream>
#include <fstream>
#include <set>
#include <stack>
#include <list>

using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

multiset<int> G[100005], Gaux[100005];

bool viz[100005], hasEven[100005];

int main()
{
    int m, n, i, j, x, y, sel;

    fin >> n >> m; sel = n;
    for(i = 1; i <= m; i++){
        fin >> x >> y;
        G[x].insert(y); G[y].insert(x);
        Gaux[x].insert(y); Gaux[y].insert(x);
        hasEven[x] = 1 - hasEven[x];
        hasEven[y] = 1 - hasEven[y];
    }

    /// Eulerian check
    stack<int> st; st.push(1); viz[1] = 1;
    while(!st.empty()){
        x = st.top();
        if(!Gaux[x].empty()){
            do{ y = *(Gaux[x].begin());
                Gaux[x].erase(Gaux[x].begin());
                Gaux[y].erase(x);
            }while(viz[y] && !Gaux[x].empty());
            if(viz[y]) st.pop();
            else st.push(y), viz[y] = 1;
        }
        else st.pop();
    }

    for(i = 1; i <= n; i++) if(viz[i] == 0 || hasEven[i] == 1) break;
    if(i <= n){ fout << -1; return 0;} /// not Eulerian

    list<int> cyc;
    list<int>::iterator here;
    st.push(1); cyc.push_back(1);
    here = cyc.begin();
    while(!st.empty()){
        x = st.top();
        if(!G[x].empty()){
            y = *(G[x].begin()); G[x].erase(G[x].begin());
            G[y].erase(G[y].find(x));
            st.push(y);
            here = cyc.insert(here, y);
        }
        else st.pop(), here++;
    }
    cyc.reverse(); cyc.pop_back();

    for(here = cyc.begin(); here != cyc.end(); here++)
        fout << *here << " ";

    return 0;
}