TREE

with open('data/rosalind_tree.txt') as input_data:
	edges = input_data.read().strip().split('\n')
	n = int(edges.pop(0))
	edges = [map(int,edge.split()) for edge in edges]


connected_nodes = [{i} for i in range(1,n+1)]

for edge in edges:
	temp_nodes = set()
	del_nodes = []
	for nodes in connected_nodes:

		
		if (edge[0] in nodes) and (edge[1] in nodes):
			break

		
		elif (edge[0] in nodes) or (edge[1] in nodes):
			
			temp_nodes.update(nodes)
			del_nodes.append(nodes)
			
			if len(del_nodes) == 2:
				break

	
	if len(del_nodes) != 0:
	
		temp_nodes.add(edge[0])
		temp_nodes.add(edge[1])
	
		for nodes in del_nodes:
			connected_nodes.remove(nodes)
	
		connected_nodes.append(temp_nodes)

print len(connected_nodes)-1
with open('output/032_TREE.txt', 'w') as output_data:
	output_data.write(str(len(connected_nodes)-1))