#include <stdio.h>
#include <fstream>
#include <list>
#include <stack>
#include <queue>
#define nmax 500001
#define NMAX 100001

using namespace std;

int N, M;
list <int> G[nmax];
int deg[NMAX];
queue <int> q;
bool viz[NMAX];
stack <int> S;
list <int> L;

int BFS (int v) {
    int count, x, y;
    list <int>::iterator it;
    q.push(v);
    viz[v] = 1;
    count = 1;
    while (!q.empty()) {
        x = q.front();
        q.pop();
        for (it = G[x].begin(); it != G[x].end(); ++it) {
            y = *it;
            if (!viz[y]) viz[y] = 1, ++count, q.push(y);
        }
    }
    if (count == N) return 1;
    return 0;
}

int eulerian () {
    for (int i = 1; i <= N; ++i)
        if (deg[i] % 2 != 0) return 0;
    return 1;
}

void sterge (int v, int w) {
    list <int>::iterator it;
    --deg[v], --deg[w];
    G[v].pop_front();
    for (it = G[w].begin(); it != G[w].end(); ++it)
        if (*it == v) {
            G[w].erase(it);
            break;
        }
}

void euler (int v) {
    while (true) {
        if (G[v].empty())
            break;
        int w = G[v].front();
        S.push(v);
        sterge (v, w);
        v = w;
    }
}

int main() {
    freopen ("ciclueuler.in", "r", stdin);
    freopen ("ciclueuler.out", "w", stdout);
    int i, x, y, ok, v;
    scanf ("%d %d", &N, &M);
    for (i = 1; i <= M; ++i) {
        scanf ("%d %d", &x, &y);
        ++deg[x];
        ++deg[y];
        G[x].push_back(y);
        G[y].push_back(x);
    }
    while (true) {
        if (!BFS(1)) {
            printf ("-1\n");
            break;
        }
        if (!eulerian()) {
            printf ("-1\n");
            break;
        }
        v = 1;
        do {
            euler( v );
            v = S.top(); S.pop();
            L.push_back (v);
        } while(!S.empty());
        list <int>::iterator it;
        for (it = L.begin(); it != L.end(); ++it)
            printf ("%d ", *it);
        printf ("\n");
        break;
    }
    return 0;
}