#include<cstdio>
#include<vector>
#include<deque>
using namespace std;
int n,m,x1,x2,x,y,i,nod;
int grad[100005];
bool viz[500005];
vector<int>v[100001],muc[100001];
deque<int>q;
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);
        muc[x].push_back(i);
        muc[y].push_back(i);
        grad[x]++;
        grad[y]++;
    }
    for(i=1;i<=n;i++)
      if((grad[i]&1)==1)
      {
          printf("-1");
          return 0;
      }
    q.push_back(1);
    while(!q.empty())
    {
        nod=q.back();
        if(grad[nod]==0)
        {
            printf("%d ",nod);
            q.pop_back();
        }
        else
        {
            x1=v[nod].back();
            x2=muc[nod].back();
            v[nod].pop_back();
            muc[nod].pop_back();
            if(viz[x2]==0)
            {
                viz[x2]=1;
                q.push_back(x1);
                grad[x1]--;
                grad[nod]--;
            }
        }
    }
    return 0;
}