#include <bits/stdc++.h>
using namespace std;

using ll = long long;

template <class comp = less<>> struct rmq {
    vector<vector<ll>> st;
    rmq(const vector<ll> &arr) : st(__lg(arr.size()) + 1) {
        st[0] = arr;
        for (int k = 1; k < st.size(); k++) {
            st[k] = st[k - 1];
            for (int i = 0; i + (1 << k) <= st[k].size(); i++) {
                ll x = st[k - 1][i + (1 << (k - 1))];
                st[k][i] = comp()(st[k][i], x) ? st[k][i] : x;
            }
        }
    }

    ll query(int l, int r) {
        int k = __lg(r - l + 1);
        ll x = st[k][l], y = st[k][r - (1 << k) + 1];
        return comp()(x, y) ? x : y;
    }
};

int main() {
    ios::sync_with_stdio(0), cin.tie(0);
    int n, q;
    cin >> n >> q;
    map<int, int> mp;
    for (int i = 0; i < n; i++) {
        int w;
        cin >> w;
        mp[w] = i;
    }
    vector<int> in(n), out(n);
    vector<ll> seq;
    vector<vector<pair<int, int>>> adj(n);
    for (int i = 0; i < n - 1; i++) {
        int u, v, w;
        cin >> u >> v >> w;
        u--, v--;
        adj[u].emplace_back(v, w);
        adj[v].emplace_back(u, w);
    }
    vector<ll> dep(n);
    int tim = 0;
    auto dfs = [&](auto self, int u, int fa) -> void {
        seq.push_back(dep[u]);
        in[u] = tim++;
        for (auto [v, w] : adj[u]) {
            if (v != fa) {
                dep[v] = dep[u] + w;
                self(self, v, u);
            }
        }
        seq.push_back(dep[u]);
        out[u] = tim++;
    };
    dfs(dfs, 0, -1);
    rmq<> rmq_seq(seq);
    auto dist = [&](int u, int v) {
        if (in[u] > in[v]) {
            swap(u, v);
        }
        return dep[u] + dep[v] - 2 * rmq_seq.query(in[u], in[v]);
    };
    vector<pair<int, int>> diam;
    int u, v;
    ll tmp;
    for (int i = 0; i < n; i++) {
        if (mp.count(i)) {
            int w = mp[i];
            if (i == 0) {
                u = v = w;
                tmp = 0;
            } else {
                ll foo = dist(u, w), bar = dist(v, w);
                if (foo >= tmp && foo >= bar) {
                    tmp = foo;
                    v = w;
                } else if (bar >= tmp && bar >= foo) {
                    tmp = bar;
                    u = w;
                }
            }
            diam.emplace_back(u, v);
        } else {
            break;
        }
    }
    while (q--) {
        int x;
        ll k;
        cin >> x >> k;
        x--;
        int l = 0, r = (int)diam.size() - 1, ans = -1;
        while (l <= r) {
            int mid = (l + r) / 2;
            auto [u, v] = diam[mid];
            if (max(dist(x, u), dist(x, v)) <= k) {
                l = (ans = mid) + 1;
            } else {
                r = mid - 1;
            }
        }
        cout << ans + 1 << "\n";
    }
    return 0;
}