import strutils,sequtils,deques

type
    edge = tuple[R,L,w : int]
var
    N = stdin.readline.parseInt
    que = initDeque[int](1024)
    ln,rn : int
    used : array[200010, bool]
    cnt : array[200010, int]
    cnte : array[200010, int]
    edges = newSeq[edge](N)
    v,u,w : int
    nodes = newSeqWith(N + 1, newSeq[int](0))
    ans : int64

for n in 0..(N - 2):
    (v,u,w) = stdin.readline.split.map(parseInt)
    v -= 1
    u -= 1
    edges[n] = (v, u, w)
    cnte[v] += 1
    cnte[u] += 1
    nodes[v].add(n)
    nodes[u].add(n)



for n in 0..<N:
    if cnte[n] == 1:
        que.addLast(nodes[n][0])
    cnt[n] = 1

while que.len > 0:
    var e1 = que.popFirst
    if used[e1]:
        continue
    var e = edges[e1]
    used[e1] = true
    if cnte[e.R] == 1:
        ans += cnt[e.R].int64 * (N - cnt[e.R]).int64 * e.w.int64
        cnt[e.L] += cnt[e.R]
    else:
        ans += cnt[e.L].int64 * (N - cnt[e.L]).int64 * e.w.int64
        cnt[e.R] += cnt[e.L]
    cnte[e.R] -= 1
    cnte[e.L] -= 1
    if cnte[e.R] == 1:
        for t in nodes[e.R]:
            if used[t] == false:
                que.addLast(t)
    elif cnte[e.L] == 1:
        for t in nodes[e.L]:
            if used[t] == false:
                que.addLast(t)
    
echo ans * 2