#include<cstdio>
#include<stack>
#include<queue>
#include<list>
using namespace std;

list<int> rez;
list<int> l[100004];
int viz[100005],deg[100004];
int n, m;
queue<int> q;
stack<int> s;
void bfs(int v)
{  q.push(v); viz[v]=1;
     while(!q.empty())
    {   int nod = q.front();
        q.pop();
        for(list<int>::iterator it = l[nod].begin(); it != l[nod].end(); it++)
            if(viz[*it] == 0)
            {   viz[*it] = 1;
                q.push(*it);
            }
    }
}

int ver_euler()
{
    bfs(1);
    for(int i = 2; i <= n; i++)
        if(viz[i] == 0)
            return 0;
    for(int i = 1; i <= n; i++)
        if(deg[i] %2 == 1)
            return 0;
    return 1;
}

void euler(int nod)
{   while(!l[nod].empty())
    {   int urm = l[nod].front();
        s.push(nod);
        l[nod].pop_front();
        deg[nod]--;
        deg[urm]--;
        for(list<int>::iterator it = l[urm].begin(); it != l[urm].end(); it++)
            if(*it == nod)
                {   l[urm].erase(it);
                    break;
                }
        nod = urm;
    }
}
int solve()
{   int var = ver_euler();
    if(var == 0)
        return -1;
    do
    {
        euler(var);
        var = s.top();
        s.pop();
        rez.push_back(var);
    }while( !s.empty() );
return 1;
}

int main()
{   freopen("ciclueuler.in", "r", stdin);
    freopen("ciclueuler.out", "w", stdout);
    scanf("%d%d", &n, &m);
    int x, y;
    for(int i = 1; i <= m; i++ )
    {
        scanf("%d%d", &x, &y);
        l[x].push_back(y);
        l[y].push_back(x);
        deg[x]++;
        deg[y]++;
    }
  if (solve() == -1) printf("-1");
  else
    for(list<int>::iterator it = rez.begin(); it != rez.end(); it++)
        printf("%d ",*it);


return 0;
}