#include<algorithm>
#include<bitset>
#include<cmath>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<ctime>
#include<deque>
#include<fstream>
#include<iomanip>
#include<iostream>
#include<map>
#include<queue>
#include<set>
#include<stack>
#include<unordered_map>
#include<unordered_set>
#include<utility>
#include<vector>

using namespace std;

#ifdef HOME
const string inputFile = "input.txt";
const string outputFile = "output.txt";
#else
const string problemName = "ciclueuler";
const string inputFile = problemName + ".in";
const string outputFile = problemName + ".out";
#endif

typedef pair<int, int> PII;
const int NMAX = 100000 + 5;
const int MMAX = 500000 + 5;

int N, M;
vector<PII> V[NMAX];
bitset<NMAX> viz;
bitset<MMAX> marked;
vector<int> S, sol;

void dfs(int x) {
    viz[x] = 1;
    for(auto y : V[x])
        if(!viz[y.first])
            dfs(y.first);
}

int eulerian() {
    int i;

    dfs(1);

    for(i = 1; i <= N; i++)
        if(!viz[i] || V[i].size() % 2)
            return 0;

    return 1;
}

void get_node(int x, int &y, int &i) {
    while(!V[x].empty() && marked[V[x].back().second])
        V[x].pop_back();

    if(!V[x].empty()) {
        y = V[x].back().first;
        i = V[x].back().second;
    } else
        y = i = 0;
}

void get_cycle() {
    int x, y, i;

    S.push_back(1);

    while(!S.empty()) {
        x = S.back();

        get_node(x, y, i);

        if(i) {
            marked[i] = 1;
            S.push_back(y);
        } else {
            sol.push_back(x);
            S.pop_back();
        }
    }

    if(sol.size() > 1)
        sol.pop_back();
}

void print_cycle() {
    for(auto x : sol)
        printf("%d ", x);
}

int main() {
    int i, x, y;

#ifndef ONLINE_JUDGE
    freopen(inputFile.c_str(), "r", stdin);
    freopen(outputFile.c_str(), "w", stdout);
#endif

    scanf("%d%d", &N, &M);

    for(i = 1; i <= M; i++) {
        scanf("%d%d", &x, &y);
        V[x].push_back(make_pair(y, i));
        V[y].push_back(make_pair(x, i));
    }

    if(eulerian()) {
        get_cycle();
        print_cycle();
    } else
        printf("-1");

    return 0;
}