# 全方位木DP
import sys
input = sys.stdin.readline
from collections import deque

mod = 10 ** 9 + 7
N = int(input())
X = [[] for i in range(N)]
for i in range(N-1):
    x, y, w = map(int, input().split())
    X[x-1].append((y-1, w))
    X[y-1].append((x-1, w))

P = [-1] * N
Q = deque([0])
R = []
D = [0] * N
while Q:
    i = deque.popleft(Q)
    R.append(i)
    for a, w in X[i]:
        if a != P[i]:
            P[a] = i
            D[a] = w
            X[a].remove((i, w))
            deque.append(Q, a)

# 
# a0 += b0
# a1 += b1 + b0 * d
# a2 += b0 * d ** 2 + 2 * b1 * d + b2

##### Settings
unit = (0, 0, 0)
merge = lambda a, b: ((a[0] + b[0]) % mod, (a[1] + b[1]) % mod, (a[2] + b[2]) % mod)

## ↓ この2つは必ず対称的にする（じゃないとバグる）
def adj_bu(a, i, p):
    a0, a1, a2 = a
    a0 += 1
    d = D[i]
    return (a0, (a1 + a0 * d) % mod, (a0 * d ** 2 + 2 * a1 * d + a2) % mod)
def adj_td(a, i, p):
    a0, a1, a2 = a
    a0 += 1
    d = D[i]
    return (a0, (a1 + a0 * d) % mod, (a0 * d ** 2 + 2 * a1 * d + a2) % mod)

adj_fin = lambda a, i: a[2]
#####

ME = [unit] * N
XX = [0] * N
TD = [unit] * N
for i in R[1:][::-1]:
    p = P[i]
    XX[i] = adj_bu(ME[i], i, p)
    ME[p] = merge(ME[p], XX[i])
XX[R[0]] = adj_fin(ME[R[0]], R[0])

for i in R:
    ac = TD[i]
    for j, _ in X[i]:
        TD[j] = ac
        ac = merge(ac, XX[j])
    ac = unit
    for j, _ in X[i][::-1]:
        TD[j] = adj_td(merge(TD[j], ac), j, i)
        ac = merge(ac, XX[j])
        XX[j] = adj_fin(merge(ME[j], TD[j]), j)

print(sum(XX) * (mod + 1) // 2 % mod)