import sys
input = sys.stdin.readline
sys.setrecursionlimit(10 ** 6)

def dfs(cur, prev):
    res = 1
    
    for next_node in adj_list[cur]:
        if next_node != prev:
            res += dfs(next_node, cur)
    
    cnt[cur] = res
    
    return res

N = int(input())
edges = []
adj_list = [[] for _ in range(N)]

for _ in range(N-1):
    ui, vi, wi = map(int, input().split())
    edges.append((ui-1, vi-1, wi))
    adj_list[ui-1].append(vi-1)
    adj_list[vi-1].append(ui-1)

cnt = [0] * N
dfs(0, None)
ans = 0

for ui, vi, wi in edges:
    if cnt[ui] > cnt[vi]:
        ans += 2 * cnt[vi] * (N - cnt[vi]) * wi
    else:
        ans += 2 * cnt[ui] * (N - cnt[ui]) * wi

print(ans)