def read_tree(line):
parents = map(int, line.split())
trees = dict()
root = None
for i in xrange(1, len(parents) + 1):
# if not trees[i-1] and parents[i-1]!=-1:
if i - 1 not in trees.keys() and parents[i - 1] != -1:
idx = i
prev = None
while True:
parent = parents[idx - 1]
if parent == -1:
break
tree = Tree()
if prev is not None:
tree.add_child(prev)
trees[idx - 1] = tree
tree.idx = idx - 1
# if trees[parent-1] is not None:
if parent - 1 in trees.keys():
trees[parent - 1].add_child(tree)
break
elif parent == 0:
root = tree
break
else:
prev = tree
idx = parent
return root
