#include<bits/stdc++.h>
using namespace std;
const int N=800005;
vector<int> bel[N];
int cur[N],from[N],S,T,ne[N],a[N],b[N],dis[N],flag[N],x,y,n,m,fi[N],tot,zz[N],sl[N];
queue<int>Q;
void jb(int x,int y,int z){
	ne[++tot]=fi[x];
	fi[x]=tot;
	zz[tot]=y;
	sl[tot]=z;
	ne[++tot]=fi[y];
	fi[y]=tot;
	zz[tot]=x;
	sl[tot]=0;
}
int bfs(){
	Q.push(S);
	memset(dis,-1,sizeof dis);
	dis[S]=0;
	while (!Q.empty()){
		int now=Q.front();Q.pop();
		for (int i=fi[now];i;i=ne[i])
			if (sl[i]&&dis[zz[i]]==-1){
				dis[zz[i]]=dis[now]+1;
				Q.push(zz[i]);
			}
	}
	return dis[T]!=-1;
}
int dfs(int x,int y){
	if (x==T)return y;
	int s=0,b;
	for (int &i=cur[x];i;i=ne[i])
		if (sl[i]&&dis[zz[i]]==dis[x]+1&&(b=min(sl[i],dfs(zz[i],min(sl[i],y))))){
			sl[i]-=b;
			sl[i^1]+=b;
			y-=b;
			s+=b;
			if (!y)return s;
		}
	return s;
}
int main(){
	scanf("%d",&n);
	S=0;T=2*n;
	tot=1;
	for (int i=1;i<n;i++){
		scanf("%d",&x);
		jb(S,i+n,1);
		while (x--){
			scanf("%d",&y);
			jb(i+n,y,1);
			bel[y].push_back(i);
		}
	}
	for (int i=1;i<=n;i++)jb(i,T,1);
	int ans=0;
	while (bfs()){
		for (int i=S;i<=T;i++)cur[i]=fi[i];
		ans+=dfs(S,1e9);
	}
	if (ans!=n-1){
		puts("-1");
		return 0;
	}
	for (int i=1;i<n;i++)
		for (int j=fi[i+n];j;j=ne[j])
			if (zz[j]&&!sl[j]){
				flag[zz[j]]=1;
				b[i]=zz[j];
			}
	for (int i=1;i<=n;i++)
		if (!flag[i])Q.push(i);
	ans=0;
	memset(flag,0,sizeof flag);
	while (!Q.empty()){
		int now=Q.front();Q.pop();
		ans++;
		for (int i=0;i<bel[now].size();i++)
			if (!flag[bel[now][i]]){
				flag[bel[now][i]]=1;
				a[bel[now][i]]=now;
				Q.push(b[bel[now][i]]);
			}
	}
	if (ans!=n){
		puts("-1");
		return 0;
	}
	for (int i=1;i<n;i++)printf("%d %d\n",a[i],b[i]);
}
