import sys
input = lambda : sys.stdin.readline().rstrip()

sys.setrecursionlimit(2*10**5+10)
write = lambda x: sys.stdout.write(x+"\n")
_print = lambda *x: print(*x, file=sys.stderr)

# グラフの読み込み
n = int(input())
ns = [[] for _ in range(n)]
M = 10**9+7
for _ in range(n-1):
    u,v,c = map(int, input().split())
    u -= 1
    v -= 1
    ns[u].append((c,v))
    ns[v].append((c,u))
# 深さ優先探索 (巻き戻しあり) dfs
q = [(0, -1)]
d = [0]*n
s = [0]*n
k = [0]*n
v1 = 0
v2 = 0
while q:
    u,prv = q.pop()
    if u<0:
        # 返るときの処理
        u = ~u
        ss = 0
        ss2 = 0
        kk = 0
        kk2 = 0
        for c,v in ns[u]:
            if v==prv:
                continue
            ss += s[v]
            ss2 += s[v]*s[v]
            kk += k[v]
            kk2 += k[v]**2
        vv1 = ((ss**2 - ss2)//2 + ss) * d[u]**2
        vv2 = 0
        for c,v in ns[u]:
            if v==prv:
                continue
            vv2 += (k[v]*(ss-s[v]))*d[u]
        vv2 += (kk+ss*d[u]) * d[u]
#         print(u,vv1,vv2, ss, ss2, kk, kk2)
        v1 += vv1
        v2 += vv2
        v1 %= M
        v2 %= M
        s[u] = ss + 1
        k[u] = kk + d[u]
    else:
        q.append((~u,prv))
        for c,v in ns[u]:
            # 進むときの処理
            if v==prv:
                continue
            q.append((v,u))
            d[v] = d[u] + c
S = 0
S2 = 0
for v in d:
    S += v
    S2 += v*v
    S%=M
    S2%=M
ans = n*S2 + S*S - 2*S2 + 4*v1 - 4*v2
print(ans%M)