class SCCGraph: def __init__(self, G): self.N = N = len(G) self.G = G self.H = [[] for _ in range(N)] for v in range(N): for a in G[v]: self.H[a].append(v) called = [False]*N closed = [False]*N preO = [] postO = [] def dfs(s): Q = [~s, s] while Q: v = Q.pop() if v >= 0: if called[v]: continue called[v] = True preO.append(v) for a in reversed(self.G[v]): if called[a]: continue Q.append(~a) Q.append(a) else: v = ~v if closed[v]: continue closed[v] = True postO.append(v) for s in range(N): if called[s]: continue dfs(s) found = [False]*N self.SCCs = SCCs = [] self.atlas = atlas = [-1]*N cur = 0 for s in reversed(postO): if found[s]: continue SCC = [] Q = [s] while Q: v = Q.pop() if found[v]: continue found[v] = True SCC.append(v) for a in self.H[v]: Q.append(a) SCCs.append(SCC) for v in SCC: atlas[v] = cur cur += 1 SCCs.reverse() for v in range(N): atlas[v] = cur-1-atlas[v] self.DAG: list|None = None def contract(self): dag = [set() for _ in range(len(self.SCCs))] for v in range(self.N): for a in self.G[v]: if self.atlas[v] == self.atlas[a]: continue dag[self.atlas[v]].add(self.atlas[a]) return [list(d) for d in dag] INF = float("INF") N = int(input()) G = [[] for _ in range(N)] for v in range(N): M, *A = map(int, input().split()) G[v] = [a-1 for a in A] sccG = SCCGraph(G) nG = sccG.contract() ns = sccG.atlas[0] nN = len(nG) in_deg = [0]*nN for nv in range(nN): for na in nG[nv]: in_deg[na] += 1 if in_deg[ns] == 0 and in_deg.count(1) == nN-1: ans = True else: ans = False if ans is True: print("Yes") else: print("No")