#include <fstream>
#include <vector>
#include <stack>
#define NMAX 100005
#define MMAX 500005

using namespace std;

FILE* f=freopen("ciclueuler.in","r",stdin);
FILE* o=freopen("ciclueuler.out","w",stdout);

int n,m;
vector<int> graph[NMAX];
vector<int> sol;
stack<int> stk;

void Erase(int x, int i)
{
    int ind=graph[x][i];
    graph[x][i]=-1;
    for(int j=0;j<graph[ind].size();++j)
    {
        if(graph[ind][j]==x) {
            graph[ind][j]=-1;
            break;
        }
    }
}

void EulerianPath(int x)
{
    int ok=1;
    while(ok) {
        ok=0;
        for(int i=0;i<graph[x].size();++i)
        {
            int ind=graph[x][i];
            if(ind!=-1)
            {
                ok=1;
                stk.push(x);
                Erase(x,i);
                x=ind;
                break;
            }
        }
    }
}

int main()
{
    scanf("%d%d",&n,&m);

    for(int i=0;i<m;++i)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        graph[x].push_back(y);
        graph[y].push_back(x);
    }
    for(int i=1;i<=n;++i) if(graph[i].size()%2||graph[i].size()==0) { printf("-1"); return 0; }

    EulerianPath(1);
    while(!stk.empty())
    {
        int x=stk.top();
        sol.push_back(x);
        stk.pop();
        EulerianPath(x);
    }

    for(int i=0;i<sol.size()-1;++i)
    {
        printf("%d ",sol[i]);
    }

    return 0;
}









#include <fstream>
#include <utility>
#include <queue>
#define l first
#define x second
#define NMAX 105
#define MMAX 1005
#define LMAX 1005

using namespace std;

FILE* f=freopen("ausoara.in","r",stdin);
FILE* o=freopen("ausoara.out","w",stdout);

typedef pair<int,int> Point;
int n;
int minp,minl=2*LMAX;
Point mat[NMAX][MMAX];
int lrow[NMAX];
int v[LMAX];
queue<Point> row;

int minim(int a, int b)
{
    return (a<b)?a:b;
}

void ReadRow(int v[])
{
    scanf("%d",&v[0]);
    for(int i=1;i<=v[0];++i)
    {
        scanf("%d",&v[i]);
    }
}

void CompressRow(Point a[], int p, int v[])
{
    int last=-1;
    int j=0;
    for(int i=1;i<=v[0];++i)
    {
        if(v[i]!=last)
        {
            a[j].l=1;
            a[j].x=v[i];
            j+=1;
        }
        else
        {
            a[j-1].l+=1;
        }
        last=v[i];
    }
    lrow[p]=j;
}

void UpdateRow(int pj)
{
    Point a=row.front();
    row.pop(); //POPED
    Point *b=mat[pj];
    int i,j;
    int l=row.size();
    for(i=0;i<l;)
    {
        for(j=0;j<lrow[pj];)
        {
            if(a.x==b[j].x)
            {
                a.l=minim(a.l,b[j].l);
                row.push(a);
                a=row.front();
                row.pop();
                i+=1;
                j+=1;
            }
            else if(a.x<b[j].x)
            {
                a=row.front();
                row.pop();
                i+=1;
            }
            else
            {
                b[j++].l=0;
            }
        }
    }
}

void WriteRow()
{
    printf("%d ",row.size());
    while(!row.empty())
    {
        printf("%d ",row.front());
        row.pop();
    }
}

int main()
{
    scanf("%d",&n);
    for(int i=0;i<n;++i)
    {
        ReadRow(v);
        CompressRow(mat[i],i,v);
        if(lrow[i]<minl)
            minl=lrow[i],minp=i;
    }
    for(int i=0;i<minl;++i)
        row.push(mat[minp][i]);
    for(int i=0;i<n;++i)
    {
        if(minp!=i)
        {
            UpdateRow(i);
        }
    }

    WriteRow();

    return 0;
}