package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func getScanner(fp *os.File) *bufio.Scanner {
	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 1000005), 1000005)
	return scanner
}
func getNextString(scanner *bufio.Scanner) string {
	scanner.Scan()
	return scanner.Text()
}
func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}
func getNextInt64(scanner *bufio.Scanner) int64 {
	i, _ := strconv.ParseInt(getNextString(scanner), 10, 64)
	return i
}
func getNextUint64(scanner *bufio.Scanner) uint64 {
	i, _ := strconv.ParseUint(getNextString(scanner), 10, 64)
	return i
}
func getNextFloat64(scanner *bufio.Scanner) float64 {
	i, _ := strconv.ParseFloat(getNextString(scanner), 64)
	return i
}
func main() {
	fp := os.Stdin
	wfp := os.Stdout
	cnt := 0
	if os.Getenv("MASPY") == "ますピ" {
		fp, _ = os.Open(os.Getenv("BEET_THE_HARMONY_OF_PERFECT"))
		cnt = 1
	}
	if os.Getenv("MASPYPY") == "ますピッピ" {
		wfp, _ = os.Create(os.Getenv("NGTKANA_IS_GENIUS10"))
	}
	scanner := getScanner(fp)
	writer := bufio.NewWriter(wfp)
	solve(scanner, writer)
	for i := 0; i < cnt; i++ {
		fmt.Fprintln(writer, "-----------------------------------")
		solve(scanner, writer)
	}
	writer.Flush()
}
func solve(scanner *bufio.Scanner, writer *bufio.Writer) {
	n := getNextInt(scanner)
	g := newGraph(n)
	for i := 0; i < n-1; i++ {
		u := getNextInt(scanner) - 1
		v := getNextInt(scanner) - 1
		w := getNextInt(scanner)
		g.appendEdge(u, v, i, w)
		g.appendEdge(v, u, i, w)
	}
	g.dfs(0, -1)
	fmt.Fprintln(writer, g.ans*2)
}

type graph struct {
	v   []*vertex
	e   [][]*edge
	ans int64
}

func newGraph(n int) *graph {
	return &graph{
		v: make([]*vertex, n),
		e: make([][]*edge, n),
	}
}
func (g *graph) dfs(c, p int) int {
	cnt := 1
	for _, e := range g.e[c] {
		if e.to == p {
			continue
		}
		ch := g.dfs(e.to, c)
		cnt += ch
		g.ans += int64(ch) * int64(len(g.v)-ch) * int64(e.w)
	}
	return cnt
}
func (g *graph) appendEdge(from, to, id, w int) {
	g.e[from] = append(g.e[from], &edge{
		to: to,
		id: id,
		w:  w,
	})
}

type vertex struct {
}
type edge struct {
	to, id, w int
}