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


def main():
    N = int(input())
    edges = [[] for _ in range(N)]
    path = []
    for _ in range(N-1):
        u, v, w = map(int, input().split())
        u -= 1
        v -= 1
        edges[u].append(v)
        edges[v].append(u)
        path.append([u,v,w])

    subtree_size = [0] * N
    def dfs(v, p):
        res = 1
        for nv in edges[v]:
            if nv == p:
                continue
            res += dfs(nv, v)
        
        subtree_size[v] = res

        return res

    dfs(0,-1)
    ans = 0
    for u, v, w in path:
        if subtree_size[u] > subtree_size[v]:
            ans += 2 * subtree_size[v] * (N - subtree_size[v]) * w
        else:
            ans += 2 * subtree_size[u] * (N - subtree_size[u]) * w
    print(ans)



if __name__ == "__main__":
    main()