import sys

read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

MOD = 1_000_000_007

def bfs_tree(N, G, root=1):
    q = [root]
    parent = [0] * (N + 1)
    dist = [0] * (N + 1)
    for v in q:
        for w, cost in G[v]:
            if w == parent[v]:
                continue
            dist[w] = dist[v] + cost
            parent[w] = v
            q.append(w)
    return parent, q, dist

def main(N, G):
    parent, order, dist = bfs_tree(N, G)
    ans = 0
    # k 乗和
    dp_0 = [0] * (N + 1)
    dp_1 = [0] * (N + 1)
    dp_2 = [0] * (N + 1)
    dp = [0] * (N + 1)  # lca ごとの答
    for v in order[::-1]:
        dp_0[v] += 1
        dp[v] += dp_2[v] * dp_0[v] * 2
        dp[v] += 2 * dp_1[v]**2

        dp_0[v] %= MOD
        dp_1[v] %= MOD
        dp_2[v] %= MOD
        dp[v] %= MOD

        p = parent[v]
        if p == 0:
            break
        d = dist[v] - dist[p]

        dp[p] -= dp_0[v] * dp_2[v] * 2 + 4 * d * d * dp_0[v]**2
        dp[p] -= 2 * dp_1[v] * dp_1[v]
        dp[p] -= 8 * d * dp_0[v] * dp_1[v]

        dp_0[p] += dp_0[v]
        dp_1[p] += dp_1[v] + d * dp_0[v]
        dp_2[p] += dp_2[v] + 2 * d * dp_1[v] + d * d * dp_0[v]

    ans = sum(dp) % MOD
    if ans & 1:
        ans += MOD
    ans //= 2
    return ans

N = int(readline())
G = [[] for _ in range(N + 1)]
for line in readlines():
    a, b, c = map(int, line.split())
    G[a].append((b, c))
    G[b].append((a, c))

print(main(N, G))