#include <fstream>
#include <vector>
#include <queue>
#include <stack>
using namespace std;

const int MAX_N = 100002;

int N, M, x, y;
int m[MAX_N], grad[MAX_N];
vector < int > ciclu, v[MAX_N];
queue < int > Q;
stack < int > st;

inline void BFS(int st)
{
    m[st] = 1, Q.push(st);
    while(!Q.empty())
    {
        int x = Q.front();
        Q.pop();
        for(int i = 0; i < v[x].size(); ++i)
        {
            int y = v[x][i];
            if(!m[y])
                m[y] = 1, Q.push(y);
        }
    }
}
inline int graf_eulerian()
{
    BFS(1);
    for(int i = 2; i <= N; ++i)
        if(!m[i])
            return 0;

    for(int i = 1; i <= N; ++i)
        if(grad[i] % 2)
            return 0;

    return 1;
}

inline void sterge_muchia(int x, int y);

inline void euler(int x)
{
    while(!v[x].empty())
    {
        int y = v[x].front();
        sterge_muchia(x, y);
        sterge_muchia(y, x);
        st.push(x);
        x = y;
    }
}

inline void sterge_muchia(int x, int y)
{
    for(int i = 0; i < v[x].size(); ++i)
        if(v[x][i] == y)
        {
            v[x].erase(v[x].begin()+i);
            return;
        }
}

int main()
{
    ifstream f("ciclueuler.in");
    ofstream g("ciclueuler.out");

    f >> N >> M;
    for(int i = 1; i <= M; ++i)
    {
        f >> x >> y;
        v[x].push_back(y), v[y].push_back(x);
        ++grad[x], ++grad[y];
    }

    if(graf_eulerian())
    {
        int x = 1;
        do
        {
            euler(x);
            x = st.top(), st.pop();
            ciclu.push_back(x);
        }while(!st.empty());

        for(int i = 0; i < ciclu.size(); ++i)
            g << ciclu[i] << " ";
    }
    else g << -1;
    g << '\n';

    f.close();
    g.close();

    return 0;
}