#include <vector>
#include <cstdio>
#include <algorithm>

#define int long long

using namespace std;

const int N = 2000005;

int n, ans, cnt, num, a[250005], b[250005], f[N], rt[250005 << 1], ls[N], rs[N], val[N], dis[N], dep[250005];

vector < pair <int, int> > e[250005];

int merge(int x, int y)
{
    if(!x || !y)
        return x + y;
    if(val[x] > val[y])
        swap(x, y);
    rs[x] = merge(rs[x], y);
    f[ls[x]] = f[rs[x]] = f[x];
    if(dis[ls[x]] < dis[rs[x]])
        swap(ls[x], rs[x]);
    dis[x] = dis[rs[x]] + 1;
    return x;
}

void del(int &x)
{
    f[ls[x]] = ls[x], f[rs[x]] = rs[x];
    x = merge(ls[x], rs[x]);
}

void dfs(int u, int fa)
{
    if(a[u] < b[u])
        for(int i = 1; i <= b[u] - a[u]; ++ i)
            val[++ cnt] = dep[u] - 1e12, rt[u] = merge(rt[u], f[cnt] = cnt), ++ num;
    if(a[u] > b[u])
        for(int i = 1; i <= a[u] - b[u]; ++ i)
            val[++ cnt] = dep[u], rt[u + n] = merge(rt[u + n], f[cnt] = cnt);
    for(auto [v, w] : e[u])
    {
        if(v == fa)
            continue;
        dep[v] = dep[u] + w;
        dfs(v, u);
        rt[u] = merge(rt[u], rt[v]);
        rt[u + n] = merge(rt[u + n], rt[v + n]);
    }
    while(rt[u] && rt[u + n] && val[rt[u]] + val[rt[u + n]] - 2 * dep[u] < 0)
    {
        int x = rt[u], y = rt[u + n], A = val[x], B = val[y];
        ans += A + B - 2 * dep[u];
        del(rt[u]), del(rt[u + n]);
        val[x] = 2 * dep[u] - B, ls[x] = rs[x] = 0;
        val[y] = 2 * dep[u] - A, ls[y] = rs[y] = 0;
        rt[u] = merge(rt[u], f[x] = x);
        rt[u + n] = merge(rt[u + n], f[y] = y);
    }
}

signed main()
{
    scanf("%lld", &n);
    for(int i = 1, u, v, w; i < n; ++ i)
    {
        scanf("%lld%lld%lld", &u, &v, &w);
        e[u].push_back({v, w});
        e[v].push_back({u, w});
    }
    for(int i = 1; i <= n; ++ i)
        scanf("%lld%lld", &a[i], &b[i]);

    dfs(1, 0);

    printf("%lld\n", ans + num * 1000000000000);

    return 0;
}