def scc(N,edges): M=len(edges) start=[0]*(N+1) elist=[0]*M for e in edges: start[e[0]+1]+=1 for i in range(1,N+1): start[i]+=start[i-1] counter=start[:] for e in edges: elist[counter[e[0]]]=e[1] counter[e[0]]+=1 visited=[] low=[0]*N Ord=[-1]*N ids=[0]*N NG=[0,0] def dfs(v): stack=[(v,-1,0),(v,-1,1)] while stack: v,bef,t=stack.pop() if t: if bef!=-1 and Ord[v]!=-1: low[bef]=min(low[bef],Ord[v]) stack.pop() continue low[v]=NG[0] Ord[v]=NG[0] NG[0]+=1 visited.append(v) for i in range(start[v],start[v+1]): to=elist[i] if Ord[to]==-1: stack.append((to,v,0)) stack.append((to,v,1)) else: low[v]=min(low[v],Ord[to]) else: if low[v]==Ord[v]: while(True): u=visited.pop() Ord[u]=N ids[u]=NG[1] if u==v: break NG[1]+=1 low[bef]=min(low[bef],low[v]) for i in range(N): if Ord[i]==-1: dfs(i) for i in range(N): ids[i]=NG[1]-1-ids[i] group_num=NG[1] counts=[0]*group_num for x in ids: counts[x]+=1 groups=[[] for i in range(group_num)] for i in range(N): groups[ids[i]].append(i) return groups _N=int(input()) edge=[] edge2 = [[] for i in range(_N)] for i in range(_N): list_=list(map(int,input().split())) for j in range(1, len(list_)): edge.append((i, list_[j]-1)) edge2[i].append(list_[j]-1) res = scc(_N, edge) # print(res) if 0 not in res[0]: print("No"); exit() for i in range(len(res)-1): # i番目と i+1番目が連結かどうか set_ = set(res[i+1]) flag = False for v in res[i]: for nv in edge2[v]: if nv in set_: flag=True if flag==False: print("No"); exit() print("Yes")