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,w])
        edges[v].append([u,w])
        path.append([u,v,w])

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

    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()