func main()
	class Node()
		+var parent: Node
		+var children: list<Node>
		+var num: int
		*func ctor()
			do me.children :: #list<Node>
		end func
		+func calcNum()
			do me.children.head()
			for i(0, ^me.children - 1)
				var child: Node :: me.children.get()
				if(child.parent =& null)
					do child.parent :: me
					do child.calcNum()
					do me.num :+ child.num
				end if
				do me.children.next()
			end for
			do me.num :+ 1
		end func
	end class
	
	var n: int :: cui@inputInt()
	var nodes: []Node :: #[n]Node
	for i(0, n - 1)
		do nodes[i] :: #Node
	end for
	var u: []int :: #[n - 1]int
	var v: []int :: #[n - 1]int
	var w: []int :: #[n - 1]int
	for i(0, n - 2)
		do u[i] :: cui@inputInt() - 1
		do v[i] :: cui@inputInt() - 1
		do w[i] :: cui@inputInt()
		do nodes[u[i]].children.add(nodes[v[i]])
		do nodes[v[i]].children.add(nodes[u[i]])
	end for
	
	do nodes[0].parent :: nodes[0]
	do nodes[0].calcNum()
	
	var ans: int :: 0
	for i(0, n - 2)
		var num1: int
		if(nodes[u[i]].parent =& nodes[v[i]])
			do num1 :: nodes[u[i]].num
		else
			do num1 :: nodes[v[i]].num
		end if
		var num2: int :: n - num1
		do ans :+ num1 * num2 * w[i]
	end for
	do ans :* 2
	do cui@print("\{ans}\n")
end func