#include <bits/stdc++.h>

using namespace std;

const int nmax = 100009;
const int mmax = 500009;

vector < int > g[nmax];
int st[mmax] , p[mmax] , mark[nmax];
int n , m , top , i , x , y , S;

int df(int x)
{
    int r = 1;
    for (int i = 0 ; i < g[x].size() ; ++i)
    {
        int y = g[x][i];
        if (mark[y]) continue;

        mark[y] = 1;
        r += df(y);
    }
    return r;
}

bool check()
{
    for (i = 1 ; i <= n ; ++i)
    if (g[i].size() % 2)
    return 0;

    if (df(1) < n) return 0;
    return 1;
}

void run(int x)
{
    while (g[x].size())
    {
        int to = g[x].back();
        g[x].pop_back();

        for (int i = 0 ; i < g[to].size() ; ++i)
        if (g[to][i] == x)
        {
            g[to].erase(g[to].begin() + i);
            break;
        }

        x = to;
        st[++top] = x;
    }
}

void euler(int x)
{
    st[++top] = x;

    while (top)
    {
        x = st[top];

        if (g[x].size()) run(x);
        else
        {
            p[++S] = x;
            top--;
        }
    }

    for (i = 1 ; i <= S - 1 ; ++i)
    printf("%d " , p[i]);
}

int main()
{
freopen("ciclueuler.in" , "r" , stdin);
freopen("ciclueuler.out" , "w" , stdout);

scanf("%d" , &n);
scanf("%d" , &m);

for (i = 1 ; i <= m ; ++i)
{
    scanf("%d" , &x);
    scanf("%d" , &y);

    g[x].push_back(y);
    g[y].push_back(x);
}

if (check())
euler(1);
else
printf("-1\n");

return 0;
}