#include <cstdio>
#include <vector>
#define mp make_pair

using namespace std;

const int N = 100010;

vector <int> v, rez;

vector <pair <int, int> > L[N];

int n, gr[N];

bool used[5 * N];

void read() {
    int m = 0, x, y, l;
    char str[105];
    freopen("ciclueuler.in", "r", stdin);
    freopen("ciclueuler.out", "w", stdout);

    gets(str);
    l = 0;
    while(str[l] != ' ') {
        n = n * 10 + str[l] - '0';
        ++ l;
    }
    ++ l;
    while(str[l] != ' ' && str[l]) {
        m = m * 10 + str[l] - '0';
        ++ l;
    }
    for (int i = 1; i <= m; ++ i) {
        gets(str);
        l = 0;
        x = y = 0;
        while(str[l] != ' ') {
            x = x * 10 + str[l] - '0';
            ++ l;
        }
        ++ l;
        while(str[l] != ' ' && str[l]) {
            y = y * 10 + str[l] - '0';
            ++ l;
        }
        L[x].push_back(mp(y,i));
        L[y].push_back(mp(x,i));
    }
}

bool verif() {
    for (int i = 1; i <= n; ++ i)
        if (L[i].size() % 2 == 1)
            return false;
    return true;
}

void ciclu_euler() {
    int nc;
    bool ok;

    v.push_back(1);

    while (! v.empty()) {
        ok = false;
        nc = *(-- v.end());

        for (vector <pair <int, int> > :: iterator it = L[nc].begin(); it != L[nc].end(); ++ it)
            if (! used[it -> second]) {
                used[it -> second] = 1;
                v.push_back(it -> first);
                ok = true;
                break;
            }

        if (ok == false) {
            rez.push_back(nc);
            v.pop_back();
        }
    }
}

void afis() {
    vector <int> :: iterator it = rez.end();
    -- it;
    for (it = it; it != rez.begin(); -- it)
        printf("%d ", *it);
}

int main() {
    read();
    if (! verif()) {
        printf("-1\n");
        return 0;
    }
    ciclu_euler();
    afis();
    return 0;
}