#include <bits/stdc++.h>

using namespace std;

#define     mp              make_pair
#define     fs              first
#define     sc              second
#define     pob             pop_back
#define     pub             push_back
#define     eps             1E-7
#define     sz(a)           a.size()
#define     count_one       __builtin_popcount;
#define     count_onell     __builtin_popcountll;
#define     fastIO          ios_base::sync_with_stdio(false)
#define     PI              (acos(-1.0))
#define     linf            (1LL<<62)//>4e18
#define     inf             (0x7f7f7f7f)//>2e9

#define DEBUG 1
#ifdef DEBUG
#define D(x) x
#else
#define D(x)
#endif

#define MAXN 100010

FILE *in = fopen("ciclueuler.in", "r");
FILE *out = fopen("ciclueuler.out", "w");

int n, m;
int deg[MAXN];
vector<int> vec[MAXN], ciclu;
bitset<MAXN> viz;

void dfs(int nod) {
    viz[nod] = 1;
    for(auto it = vec[nod].begin(); it != vec[nod].end(); ++it)
        if(!viz[*it])
            dfs(*it);
}

bool isConex() {
    dfs(1);
    for(int i = 1; i <= n; ++i)
        if(!viz[i])
            return false;

    return true;
}

bool isEuler() {
    if(!isConex())
        return false;

    for(int i = 1; i <= n; ++i)
        if(deg[i] % 2)
            return false;

    return true;
}

void euler(int nod) {
    int x;
    while(!vec[nod].empty()) {
        x = *vec[nod].begin();
        vec[nod].erase(vec[nod].begin());
        for(auto it = vec[x].begin(); it != vec[x].end(); it++)
            if(*it == nod) {
                vec[x].erase(it);
                break;
            }
        euler(x);
    }
    ciclu.pub(nod);
}

void solve() {
    if(isEuler()) {
        euler(1);
        for(auto it = ciclu.begin(); it != ciclu.end(); it++) {
            fprintf(out, "%d ", *it);
        }
    } else {
        fprintf(out, "-1\n");
    }
}

int main()
{
    int x, y;

    fscanf(in, "%d%d", &n, &m);
    for(int i = 0; i < m; ++i) {
        fscanf(in, "%d%d", &x, &y);
        vec[x].pub(y); deg[x]++;
        vec[y].pub(x); deg[y]++;
    }

    solve();

    return 0;
}