#include<cstdio>
#include<vector>
using namespace std;
int n,i,j,m,nrv[100001],cate,vec[500001];
vector<int> v[100001],vc[100001];
void dfs(int nod)
    {
    if(cate<m)
        vec[++cate]=nod;
    int i;
    for(i=0;i<v[nod].size();i++)
        if(vc[nod][i]==0&&nrv[v[nod][i]]!=1)
            {
            vc[nod][i]=1;
            nrv[v[nod][i]]--;
            nrv[nod]--;
            int i1=v[nod][i];
            for(int j=0;j<v[i1].size();j++)
                if(vc[i1][j]==0&&v[i1][j]==nod)
                    {
                    vc[i1][j]=1;
                    break;
                    }
            dfs(v[nod][i]);
            break;
            }
    }
int main ()
{
freopen("ciclueuler.in","r",stdin);
freopen("ciclueuler.out","w",stdout);
scanf("%d%d",&n,&m);
int x,y;
for(i=1;i<=m;i++)
    {
    scanf("%d%d",&x,&y);
    v[x].push_back(y);
    vc[x].push_back(0);
    v[y].push_back(x);
    vc[y].push_back(0);
    nrv[x]++;
    nrv[y]++;
    }
dfs(1);
if(cate!=m)
    printf("-1");
else
    for(i=1;i<=cate;i++)
        printf("%d ",vec[i]);
return 0;
}