#include <cstdio>
#include <algorithm>
#include <vector>
#include <deque>
#define NMAX 100001
#define NODES 500010
#define pb push_back

using namespace std;

FILE *f = freopen("ciclueuler.in", "r", stdin);
FILE *g = freopen("ciclueuler.out", "w", stdout);

vector <int> G[NMAX];
vector <int> q;
int rez[NODES];
int n, m, lg;

void read() {
    scanf("%d%d", &n, &m);
    for(int i = 1; i<=m; i++)
    {
        int x, y;
        scanf("%d%d", &x, &y);
        G[x].pb(y);
        G[y].pb(x);
    }
}
int has_cycle()
{
    for(int i = 1; i<=n; i++)
        if(G[i].size() % 2 == 1) return 0;
    return 1;
}
void solve() {
    q.pb(1);
    while(!q.empty()) {
        int nod = q.back();
        if(!G[nod].empty()) {
            int new_node = G[nod].back();
            G[nod].pop_back();
            G[new_node].erase(find(G[new_node].begin(), G[new_node].end(), nod));
            q.pb(new_node);
        }
        else {
            rez[++lg] = nod;
            q.pop_back();
        }
    }
}
void write_sol() {
    if(has_cycle()) {
        solve();
        for(int i = 1; i<lg - 1; i++)
            printf("%d ", rez[i]);
    }
    else printf("%d", -1);

}
int main() {
    read();
    solve();
    write_sol();
    return 0;
}