import sys import typing class CSR: def __init__( self, n: int, edges: typing.List[typing.Tuple[int, int]]) -> None: self.start = [0] * (n + 1) self.elist = [0] * len(edges) for e in edges: self.start[e[0] + 1] += 1 for i in range(1, n + 1): self.start[i] += self.start[i - 1] counter = self.start.copy() for e in edges: self.elist[counter[e[0]]] = e[1] counter[e[0]] += 1 class _SCCGraph: ''' Reference: R. Tarjan, Depth-First Search and Linear Graph Algorithms ''' def __init__(self, n: int) -> None: self._n = n self._edges: typing.List[typing.Tuple[int, int]] = [] def num_vertices(self) -> int: return self._n def add_edge(self, from_vertex: int, to_vertex: int) -> None: self._edges.append((from_vertex, to_vertex)) def scc_ids(self) -> typing.Tuple[int, typing.List[int]]: g = CSR(self._n, self._edges) now_ord = 0 group_num = 0 visited = [] low = [0] * self._n order = [-1] * self._n ids = [0] * self._n sys.setrecursionlimit(max(self._n + 1000, sys.getrecursionlimit())) def dfs(v: int) -> None: nonlocal now_ord nonlocal group_num nonlocal visited nonlocal low nonlocal order nonlocal ids low[v] = now_ord order[v] = now_ord now_ord += 1 visited.append(v) for i in range(g.start[v], g.start[v + 1]): to = g.elist[i] if order[to] == -1: dfs(to) low[v] = min(low[v], low[to]) else: low[v] = min(low[v], order[to]) if low[v] == order[v]: while True: u = visited[-1] visited.pop() order[u] = self._n ids[u] = group_num if u == v: break group_num += 1 for i in range(self._n): if order[i] == -1: dfs(i) for i in range(self._n): ids[i] = group_num - 1 - ids[i] return group_num, ids def scc(self) -> typing.List[typing.List[int]]: ids = self.scc_ids() group_num = ids[0] counts = [0] * group_num for x in ids[1]: counts[x] += 1 groups: typing.List[typing.List[int]] = [[] for _ in range(group_num)] for i in range(self._n): groups[ids[1][i]].append(i) return groups class SCCGraph: def __init__(self, n: int = 0) -> None: self._internal = _SCCGraph(n) def add_edge(self, from_vertex: int, to_vertex: int) -> None: n = self._internal.num_vertices() assert 0 <= from_vertex < n assert 0 <= to_vertex < n self._internal.add_edge(from_vertex, to_vertex) def scc(self) -> typing.List[typing.List[int]]: return self._internal.scc() N = int(input()) M, A = [], [] scc = SCCGraph(N) for i in range(N): m, *a = map(lambda x: int(x)-1, input().split()) M.append(m) A.append(a) for j in a: scc.add_edge(i, j) scc = scc.scc() label = [-1]*N for i, l in enumerate(scc): for j in l: label[j] = i to = [set() for _ in range(len(scc))] for i in range(N): for j in A[i]: if label[i] != label[j]: to[label[i]].add(label[j]) from collections import deque q = deque([label[0]]) dist = [-1] * len(scc) dist[label[0]] = 0 while q: v = q.popleft() for u in to[v]: if dist[u] < dist[v] + 1: dist[u] = dist[v] + 1 q.append(u) print('Yes' if max(dist) == len(scc)-1 else 'No')