n = int(input())
g = [[] for _ in range(n)]
for i in range(n-1):
    a,b,c = [int(i) for i in input().split()]
    g[a-1].append((b-1,c))
    g[b-1].append((a-1,c))

q = [0]*n
parent = [-1]*n
dist = [0]*n
idx = 0
for i in range(n):
    v = q[i]
    for c,wt in g[v]:
        if c != parent[v]:
            idx += 1
            q[idx] = c
            parent[c] = v
            dist[c] = wt

sum1 = [0]*n
sum2 = [0]*n
cnt = [1]*n
MOD = 10**9+7
ans = 0
for v in q[::-1]:
    if v==0: continue
    d = dist[v]
    sum2[v] += 2*d*sum1[v]+(d**2)%MOD*cnt[v]
    sum2[v] %= MOD
    sum1[v] += d*cnt[v]
    sum1[v] %= MOD
    p = parent[v]
    ans += cnt[p]*sum2[v] + cnt[v]*sum2[p] + 2*sum1[v]*sum1[p]
    ans %= MOD
    cnt[p] += cnt[v]
    sum1[p] += sum1[v]
    sum1[p] %= MOD
    sum2[p] += sum2[v]
    sum2[p] %= MOD
print(ans)