class Tree():
    def __init__(self, n):
        self.n = n
        self.tree = [[] for _ in range(n)]
        self.cost = dict()
        self.root = None

    def add_edge(self, u, v, c):
        if u > v: u, v = v, u
        self.tree[u].append(v)
        self.tree[v].append(u)
        self.cost[u * self.n + v] = c

    def get_cost(self, u, v):
        if u < v:
            return self.cost[u * self.n + v]
        else:
            return self.cost[v * self.n + u]

    def set_root(self, r=0):
        self.root = r
        self.par = [None] * self.n
        self.ord = [r]
        stack = [r]
        while stack:
            v = stack.pop()
            for adj in self.tree[v]:
                if self.par[v] == adj: continue
                self.par[adj] = v
                self.ord.append(adj)
                stack.append(adj)


    def rerooting(self, op, e, merge, id):
        if self.root is None: self.set_root()
        dp = [e] * self.n
        lt = [id] * self.n
        rt = [id] * self.n
        inv = [id] * self.n
        for v in self.ord[::-1]:
            tl = tr = e
            for adj in self.tree[v]:
                if self.par[v] == adj: continue
                lt[adj] = tl
                self.w = self.get_cost(v, adj)
                tl = op(tl, dp[adj])
            for adj in self.tree[v][::-1]:
                if self.par[v] == adj: continue
                rt[adj] = tr
                self.w = self.get_cost(v, adj)
                tr = op(tr, dp[adj])
            dp[v] = tr
        for v in self.ord:
            if v == self.root: continue
            p = self.par[v]
            if p != self.root:
                pp = self.par[p]
                self.w = self.get_cost(p, pp)
                inv[v] = op(merge(lt[v], rt[v]), inv[p])
            else:
                inv[v] = merge(lt[v], rt[v])
            self.w = self.get_cost(v, p)
            dp[v] = op(dp[v], inv[v])
        return dp

import io, os
input = io.BytesIO(os.read(0, os.fstat(0).st_size)).readline

MOD = 1000000007

N = int(input())

t = Tree(N)

for _ in range(N - 1):
    u, v, w = map(int, input().split())
    u -= 1; v -= 1
    t.add_edge(u, v, w)

e = (1, 0, 0)

def op(p, c):
    ps, pd, pds = p
    cs, cd, cds = c
    size = ps + cs
    w = t.w
    dist = pd + cd + w * cs
    dsq = (pds + cds + w**2 * cs + 2 * w * cd) % MOD
    return size, dist, dsq

id = (0, 0, 0)

def merge(lt, rt):
    ls, ld, lds = lt
    rs, rd, rds = rt
    size = ls + rs - 1
    dist = ld + rd
    dsq = (lds + rds) % MOD
    return size, dist, dsq

dp = t.rerooting(op, e, merge, id)

res = 0

for size, dist, dsq in dp:
    res += dsq
    res %= MOD

print(res * pow(2, MOD - 2, MOD) % MOD)