// https://szkopul.edu.pl/problemset/problem/89019WebQziwBUs7fTVV_lrA/site/?key=statement

#include <bits/stdc++.h>
#include <sys/resource.h>

using namespace std;

#define int long long

constexpr int sizik = 1000 * 1001, INF = INT64_MAX, NINF = INT64_MIN;

#define ar std::array
#define pr std::pair
#define vec std::vector

typedef vec<vec<int>> _kra;

int a[sizik];
std::map<std::pair<int, int>, int> m;
std::vector<int> kra[sizik];
int type[sizik], value[sizik], dp[sizik];

void DFS(int v, int p) {
    int S = a[v], M = -1;
    std::vector<int> dod;
    for (const auto& u : kra[v]) {
        if (u != p) {
            DFS(u, v);
            dp[v] += dp[u];
            if (type[u] == 1) {
                S += value[u];
            } else if (type[u] == 2) {
                dod.push_back(u);
            }
        }
    }

    for (const auto& u : dod) {
        M = std::max(M, std::min(value[u] - S, m[{u, v}] - S));
    }

    if (M >= 0) {
        type[v] = 2;
        value[v] = M;
    } else {
        if (S <= m[{v, p}]) {
            type[v] = 1;
            value[v] = S;
        } else {
            type[v] = 2;
            value[v] = m[{v, p}];
            dp[v]++;
        }
    }
}

void solve() {
    int n;
    std::cin >> n;

    for (int i = 1; i <= n; i++) {
        std::cin >> a[i];
    }

    m[{1, 1}] = NINF;

    for (int i = 0; i < n - 1; i++) {
        int a, b, c;
        std::cin >> a >> b >> c;

        m[{a, b}] = c;
        m[{b, a}] = c;

        kra[a].push_back(b);
        kra[b].push_back(a);
    }

    DFS(1, 1);

    std::cout << dp[1] << '\n';
}

int32_t main() {
    std::ios_base::sync_with_stdio(0);
    std::cin.tie(0);
    std::cout.tie(0);

    const rlim_t kStackSize = 256 * 1024 * 1024; // min stack size = 16 MB
    struct rlimit rl;
    int result;

    result = getrlimit(RLIMIT_STACK, &rl);
    if (result == 0) {
        if (rl.rlim_cur < kStackSize) {
            rl.rlim_cur = kStackSize;
            result = setrlimit(RLIMIT_STACK, &rl);
        }
    }

    int t = 1;
    // std::cin >> t;

    for (; t > 0; t--) {
        solve();
    }

    return 0;
}