import sys
sys.setrecursionlimit(10 ** 9)

n = int(input())
edges = [[] for _ in range(n)]
for _ in range(n - 1):
    u, v, w = map(int, input().split())
    u -= 1
    v -= 1
    edges[u].append((v, w))
    edges[v].append((u, w))
    
child = [1] * n
ans = 0
def dfs(pos, bpos):
    global ans
    for npos, w in edges[pos]:
        if npos == bpos:
            continue
        dfs(npos, pos)
        ans += child[npos] * (n - child[npos]) * w
        child[pos] += child[npos]
        
dfs(0, -1)
print(ans * 2)