#include<cstdio>
#include<cstring>
#include<algorithm>
#include<vector>
#include<cassert>
#include<cmath>
#include<set>
#include<utility>
#define eb emplace_back

using namespace std;
const int maxn=2.5e5+10, inf=1e9+10;
const double eps=1e-10;
typedef long long LL;
typedef pair<int, int> pii;

inline int read() {
    int x=0, f=1; char c=getchar();
    for(; c<'0'||c>'9'; c=getchar()) if(c=='-') f=0;
    for(; c>='0'&&c<='9'; c=getchar()) x=x*10+c-'0';
    return f?x:-x;
}
struct pj{
    int y, nxt, d;
} g[maxn<<1];
int len, la[maxn];
inline void add_e(int x, int y, int d) {g[++len].y=y; g[len].nxt=la[x]; la[x]=len; g[len].d=d;}
int a[maxn]; LL dis[maxn];

void dfs(int x, int F) {
    for(int i=la[x]; i; i=g[i].nxt) {
        int y=g[i].y;
        if(y!=F) dis[y]=dis[x]+g[i].d, dfs(y, x);
    }
}
const LL M=5e12;
//small
multiset<LL> up[maxn], dn[maxn];

inline void merge(multiset<LL>& x, multiset<LL>& y) {
    if(x.size()<y.size()) swap(x, y);
    for(auto t:y) x.insert(t);
    y.clear();
}
LL ans;
void sol(int x, int F) {
   // printf("x=%d dis[x]=%lld\n", x, dis[x]);
    for(int i=la[x]; i; i=g[i].nxt) {
        int y=g[i].y;
        if(y!=F) sol(y, x), merge(up[x], up[y]), merge(dn[x], dn[y]);
    }
    if(a[x]>0) {
        for(int i=1; i<=a[x]; ++i) up[x].insert(dis[x]);
    } else if(a[x]<0) {
        for(int i=1; i<=-a[x]; ++i) dn[x].insert(dis[x]-M);
    }
    while(up[x].size()&&dn[x].size()) {
        LL u=*up[x].begin(), v=*dn[x].begin();
        if(u+v-2*dis[x]>=0) break;
        ans+=u+v-2*dis[x];
        up[x].erase(up[x].begin()); up[x].insert(2*dis[x]-v);
        dn[x].erase(dn[x].begin()); dn[x].insert(2*dis[x]-u);
    }
}

int main() {
    int n=read();
    for(int i=1, x, y, d; i<n; ++i) {
        x=read(), y=read(), d=read();
        add_e(x, y, d); add_e(y, x, d);
    }
    int s=0;
    for(int i=1; i<=n; ++i) {
        a[i]=read(), a[i]-=read();
        if(a[i]<0) s+=-a[i];
    }
    dfs(1, 0);
    sol(1, 0);
    printf("%lld", ans+M*s);
    return 0;
}