#include <iostream>#include <cstdio>#include <string>#include <cstring>#include <queue>using namespace std;queue<int>q;#define maxn 1002struct TT{int sun[maxn];}St[maxn];int Max;int ans;bool vis[maxn];int dis[maxn];int N;bool BFS(int n){while(!q.empty())q.pop();vis[n]=1;dis[n]=0;q.push(n);while(!q.empty()){int u=q.front();q.pop();Max=Max>dis[u]?Max:dis[u];for(int k=0;St[u].sun[k]!=-1;k++){int G=St[u].sun[k];if(!vis[G]){dis[G]=dis[u]+1;vis[G]=1;q.push(G);}}}for(int i=1;i<=N;i++)if(!vis[i])return false;return true;}int main(){int n;int num;int sunnum;for(;scanf("%d",&n)==1;){ N=n;ans=-1;int LL;memset(St,-1,sizeof(St));for(int i=1;i<=n;i++){sunnum=0;scanf("%d",&num);for(int j=0;j<num;j++){scanf("%d",&St[i].sun[sunnum++]);}}for(int i=1;i<=n;i++){Max=-1;memset(vis,false,sizeof(vis));if(BFS(i)){if(Max>=ans){ans=Max;LL=i;}}}if(ans==-1){printf("impossiblen");}else{printf("%dn%dn",ans,LL);}}return 0;}
