ALGO(G,X,u,v)
INIT(G)
dfs_visit(G,u,c1)
for each x in X do
	if c1[x]=nero then
		dfs_visit(G,x,c1)
dfs_visit(GT,v,c2)
for each x in X do
	if c3[x]=nero then
		dfs_visit(GT,x,c2)
if c1[v]=nero && c2[u]=nero then
	return true
return false