Example 1

n == parent.length2 <= n <= 20000 <= parent[i] <= n - 1 for i != 0parent[0] == -10 <= num <= n - 11 <= user <= 104parent represents a valid tree.At most 2000 calls in total will be made to lock, unlock, and upgrade.Example 1

n == parent.length2 <= n <= 20000 <= parent[i] <= n - 1 for i != 0parent[0] == -10 <= num <= n - 11 <= user <= 104parent represents a valid tree.At most 2000 calls in total will be made to lock, unlock, and upgrade.