#include <bits/stdc++.h>
#define int long long
using namespace std;
int n;
int l[41234], r[41234];
int a[41234], b[41234], c[41234];
int f[41234][55][55];
//到了 u，删了 x 条左、y 条 右
int dfs(int u, int x, int y)
{
    if (u >= n)
        return c[u] * (a[u] + x) * (b[u] + y);
    if (f[u][x][y] != 0)
        return f[u][x][y];
    f[u][x][y] = min(dfs(l[u], x, y) + dfs(r[u], x, y + 1),
                     dfs(r[u], x, y) + dfs(l[u], x + 1, y));
    return f[u][x][y];
}
signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n;
    for (int i = 1; i <= n - 1; i++)
    {
        cin >> l[i] >> r[i];
        if (l[i] <= 0)
            l[i] = n - 1 - l[i];
        if (r[i] <= 0)
            r[i] = n - 1 - r[i];
    }
    for (int i = 1; i <= n; i++)
        cin >> a[n - 1 + i] >> b[n - 1 + i] >> c[n - 1 + i];
    cout << dfs(1, 0, 0) << endl;
    return 0;
}