#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <ctime>
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <deque>

#define INF ( (1 << 30) - 1 + (1 << 30) )
#define mod 666013

using namespace std;
int n, m, i, x, y, start;
vector <int> r, v[100005];
vector <int> :: iterator it;

void ERS(int x, int y)
{
    vector <int> :: iterator it;
    for(it = v[x].begin(); it != v[x].end(); it++)
        if( (*it) == y )
        {
            v[x].erase( it );
            return;
        }
}

void euler(int nod)
{
    while(v[nod].size())
    {
        int nxt = v[nod][0];
        v[nod].erase( v[nod].begin() );
        ERS(nxt, nod);
        euler(nxt);
    }
    r.push_back(nod);
}

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

    scanf("%d%d", &n, &m);
    for(i = 1; i <= m; i++)
    {
        scanf("%d%d", &x, &y);
        v[x].push_back(y);
        v[y].push_back(x);
    }

    for(i = 1; i <= n; i++)
        if(v[i].size() % 2 == 1)
        {
            printf("-1");
            return 0;
        }

    start = 1;
    while(v[start].size() == 0)
        start++;

    euler(start);
    r.erase( r.begin() + r.size() - 1 );

    for(it = r.begin(); it != r.end(); it++)
        printf("%d ", (*it) );
    return 0;
}