# include <cstdio>
# include <vector>
using namespace std;

const char *FIN = "ciclueuler.in", *FOU = "ciclueuler.out";
const int MAX_N = 100005, MAX_X = 500005;

vector <int> G[MAX_N], sol;
bool viz[MAX_X];
int N, M, X[MAX_X], Y[MAX_X];

inline void dfs (int S) {
    for (vector <int> :: iterator it = G[S].begin (); it != G[S].end (); ++it)
        if (viz[*it] == 0)
            viz[*it] = 1, dfs (X[*it] + Y[*it] - S);
    sol.push_back (S);
}

int main (void) {
    freopen (FIN, "r", stdin);
    freopen (FOU, "w", stdout);

    scanf ("%d %d", &N, &M);
    for (int i = 1; i <= M; ++i) {
        scanf ("%d %d", X + i, Y + i);
        G[X[i]].push_back (i);
        G[Y[i]].push_back (i);
    }
    for (int i = 1; i <= N; ++i) {
        if (G[i].size () & 1) {
            printf ("-1");
            return 0;
        }
    }
    dfs (1);
    for (vector <int> :: iterator it = sol.end () - 1; it != sol.begin (); --it) {
        printf ("%d ", *it);
    }
}