#include <bits/stdc++.h>
using i64 = long long;
const int N = 2.5e5, M = 8e6;
const i64 Inf = 1e12;
int n, a[N + 5];
std::vector<std::pair<int, int>> v[N + 5];
i64 ans;
struct Leftist_Tree {
    struct Node { int ls, rs, siz, d; i64 val; }ar[M + 5];
    int tot;
    int merge(int x, int y) {
        if (!x or !y) return x + y;
        if (ar[x].val > ar[y].val) std::swap(x, y);
        ar[x].rs = merge(ar[x].rs, y);
        if (ar[ar[x].rs].d > ar[ar[x].ls].d) std::swap(ar[x].ls, ar[x].rs);
        ar[x].d = ar[ar[x].rs].d + 1;
        ar[x].siz = ar[ar[x].ls].siz + ar[ar[x].rs].siz + 1;
        return x;
    }
    void insert(int &x, i64 v) {
        ar[++tot].val = v, ar[tot].siz = 1, ar[tot].d = 1, x = merge(x, tot);
    }
    void erase(int &x) { x = merge(ar[x].ls, ar[x].rs); }
    int size(int x) { return ar[x].siz; }
    i64 top(int x) { return ar[x].val; }
}tr;
int rta[N + 5], rtb[N + 5];
std::vector<i64> ar, br;
i64 dep[N + 5];
void dfs(int x, int fa) {
    for (auto [i, c] : v[x]) if (i != fa) {
        dep[i] = dep[x] + c, dfs(i, x);
        rta[x] = tr.merge(rta[x], rta[i]), rtb[x] = tr.merge(rtb[x], rtb[i]);
    }
    for (int i = 1; i <= std::abs(a[x]); ++i) {
        if (a[x] > 0) tr.insert(rta[x], dep[x]);
        else tr.insert(rtb[x], dep[x] - Inf);
    }
    while (tr.size(rta[x]) and tr.size(rtb[x])) {
        i64 p = tr.top(rta[x]), q = tr.top(rtb[x]);
        if (p + q - 2 * dep[x] < 0) {
            ans += p + q - 2 * dep[x];
            ar.push_back(2 * dep[x] - q), br.push_back(2 * dep[x] - p);
            tr.erase(rta[x]), tr.erase(rtb[x]);
        }else break;
    }
    for (auto i : ar) tr.insert(rta[x], i);
    for (auto i : br) tr.insert(rtb[x], i);
    ar.clear(), br.clear();
}
int main() {
    std::ios::sync_with_stdio(false), std::cin.tie(0), std::cout.tie(0);
    std::cin >> n;
    for (int i = 1, x, y, z; i < n; ++i) {
        std::cin >> x >> y >> z;
        v[x].push_back({y, z}), v[y].push_back({x, z});
    }
    for (int i = 1, x, y; i <= n; ++i) {
        std::cin >> x >> y, a[i] = x - y;
        if (a[i] < 0) ans -= a[i] * Inf;
    }
    dfs(1, 0), std::cout << ans << "\n";
    return 0;
}