import sys
input = sys.stdin.readline
sys.setrecursionlimit(10 ** 8)

def dfs(cur, prev):
    if cur < 0 or cur >= N:
        exit()
        
    if memo[cur] != -1:
        return memo[cur]
        
    res = 1
    
    
    memo[cur] = res
    return res
    
N = int(input())
adj_list = [[] for _ in range(N)]
edges = []

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, wi))
    adj_list[vi-1].append((ui-1, wi))

memo = [-1] * N
dfs(0, None)
ans = 0

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