import sys

sys.setrecursionlimit(10**7)

n = int(input())
uvw = [[] for i in range(n)]
ki = []
for i in range(n-1):
    u,v,w = map(int,input().split())
    u -= 1
    v -= 1
    uvw[u].append([v,w])
    uvw[v].append([u,w])
    ki.append([u,v,w])

li = [1]*n

def dfs(v,pre):
    global li
    for V,w in uvw[v]:
        if V == pre:
            continue
        li[v] += dfs(V,v)
    return li[v]

dfs(0,-1)

ans = 0

for i in range(n-1):
    u,v,w = ki[i]
    val = min(li[u],li[v])
    ans += w*val*(n-val)

print(ans*2)