# nadare様のコード参考
# https://yukicoder.me/submissions/374115

N = int(input())
size = [1] * N
depth = [-1] * N

G = [[] for i in range(N)]
E = []
for i in range(N - 1):
    a, b, w = map(int, input().split())
    a, b = a - 1, b - 1
    G[a].append([b, w])
    G[b].append([a, w])
    E.append([a, b, w])


depth[0] = 0
visited = [False] * N
stack = [0]
rev_follow = []
while stack:
    n = stack.pop()
    visited[n] = True

    for to, w in G[n]:
        if visited[to]:
            continue

        stack.append(to)
        depth[to] = depth[n] + 1
        rev_follow.append([n, to])

while rev_follow:
    a, b = rev_follow.pop()
    size[a] += size[b]

ans = 0
for a, b, w in E:
    if depth[a] < depth[b]:
        a, b = b, a
    ans += 2 * w * size[a] * (N - size[a])

print(ans)