import sys

sys.setrecursionlimit(200050)
N = int(input())
UVW = [list(map(int, input().split())) for _ in range(N - 1)]
E = [set() for _ in range(N)]
D = [0] * N
for u, v, w in UVW:
    u -= 1
    v -= 1
    E[u].add((v))
    E[v].add((u))

dp = [1] * N


def dfs(x, p):
    ret = 1
    for y in E[x]:
        if y != p:
            ret += dfs(y, x)
    dp[x] = ret
    return ret


dfs(0, -1)
ans = 0
for u, v, w in UVW:
    u -= 1
    v -= 1
    m = min(dp[u], dp[v])
    ans += w * m * (N - m)
ans *= 2
print(ans)