#include<bits/stdc++.h>
#define LL long long
#define db long double

using namespace std;
const int N=1e6+10,inf=1e9;
int rd()
{
    int x=0,w=1;char ch=0;
    while(ch<'0'||ch>'9'){if(ch=='-') w=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+(ch^48);ch=getchar();}
    return x*w;
}
int to[N],nt[N],c[N],hd[N],tot=1;
void adde(int x,int y,int z)
{
    ++tot,to[tot]=y,nt[tot]=hd[x],c[tot]=z,hd[x]=tot;
    ++tot,to[tot]=x,nt[tot]=hd[y],c[tot]=0,hd[y]=tot;
}
int ps,pt,lv[N],nhd[N];
queue<int> q;
bool bfs()
{
    memset(lv,0,sizeof(int)*(pt+1));
    lv[ps]=1,q.push(ps);
    while(!q.empty())
    {
	int x=q.front();
	q.pop();
	for(int i=hd[x];i;i=nt[i])
	{
	    int y=to[i];
	    if(c[i]>0&&!lv[y])
		lv[y]=lv[x]+1,q.push(y);
	}
    }
    return lv[pt];
}
int dfs(int x,int fw)
{
    if(x==pt) return fw;
    int an=0;
    for(int &i=nhd[x];i;i=nt[i])
    {
	int y=to[i];
	if(c[i]>0&&lv[y]==lv[x]+1)
	{
	    int dt=dfs(y,min(c[i],fw));
	    c[i]-=dt,c[i^1]+=dt;
	    fw-=dt,an+=dt;
	    if(!fw) break;
	}
    }
    return an;
}
int dinic()
{
    int an=0;
    while(bfs())
    {
	memcpy(nhd,hd,sizeof(int)*(pt+1));
	an+=dfs(ps,inf);
    }
    return an;
}
int n,an[N][2],ta,fe[N],mat[N],mk[N];
bool v[N];
void dd(int x)
{
    v[x]=1;
    for(int i=hd[x];i;i=nt[i])
    {
	int yy=to[i]-n,y=mat[to[i]];
	if(!y||v[y]||c[i]) continue;
	++ta,an[yy][0]=x,an[yy][1]=y;
	dd(y);
    }
}

int main()
{
    n=rd();
    ps=0,pt=n+n;
    for(int i=1;i<n;++i)
    {
	adde(ps,i+n,1);
	int t=rd();
	while(t--) adde(i+n,rd(),1);
    }
    for(int i=1;i<=n;++i) adde(i,pt,1),fe[i]=tot;
    if(dinic()<n-1){puts("-1");exit(0);}
    for(int i=1;i<n;++i)
    {
	for(int j=hd[i+n];j;j=nt[j])
	{
	    int y=to[j];
	    if(!c[j]&&y>=1&&y<=n){mat[i+n]=y,mk[y]=1;break;}
	}
    }
    int rt=1;
    while(mk[rt]) ++rt;
    dd(rt);
    if(ta<n-1){puts("-1");return 0;}
    for(int i=1;i<=ta;++i) printf("%d %d\n",an[i][0],an[i][1]);
    return 0;
}
 
