# include <bits/stdc++.h>

using namespace std;

namespace lyre {
  void main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n, m;
    cin >> n >> m;
    auto Lg = __lg(n);
    vector<int> w(n), dfn(n);
    vector<int> parent(n);
    vector<long> dep(n);
    vector<vector<pair<int, int>>> st(Lg + 1, vector<pair<int, int>>(n));
    vector<vector<pair<int, int>>> G(n);
    for (int i = 0; i < n; ++i)
      cin >> w[i];
    for (int i = 1; i < n; ++i) {
      int u, v, w;
      cin >> u >> v >> w;
      --u, --v;
      G[u].emplace_back(v, w);
      G[v].emplace_back(u, w);
    }
    auto index = 0;
    auto dfs = [&] (auto self, int x, int o) -> void {
      parent[x] = o;
      dfn[x] = index++;
      for (auto [y, w] : G[x]) {
        if (y == o) continue;
        dep[y] = dep[x] + w;
        self(self, y, x);
      }
    };
    dfs(dfs, 0, -1);
    for (int i = 0; i < n; ++i)
      st[0][dfn[i]] = make_pair(dfn[i], dfn[parent[i]]);
    for (int i = 0; i < Lg; ++i) {
      for (int j = 0; j + (1 << (i + 1)) - 1 < n; ++j)
        st[i + 1][j] = min(st[i][j], st[i][j + (1 << i)]);
    }
    auto lca = [&] (int x, int y) -> int {
      if (x == y) return x;
      x = dfn[x], y = dfn[y];
      if (x > y) swap(x, y);
      auto k = __lg(y - x++);
      return min(st[k][x], st[k][y - (1 << k) + 1]).second;
    };
    auto dis = [&] (int x, int y) -> long {
      return dep[x] + dep[y] - 2 * dep[lca(x, y)];
    };
    vector<int> ord(n);
    vector<pair<int, int>> g(n);
    iota(ord.begin(), ord.end(), 0);
    auto comp = [&] (int x, int y) -> bool {
      return w[x] < w[y];
    };
    sort(ord.begin(), ord.end(), comp);
    auto hi = 0;
    for (; hi < n && w[ord[hi]] == hi; ++hi);
    auto p = ord[0], q = ord[0];
    g[0] = make_pair(p, q);
    for (int i = 1; i < hi; ++i) {
      auto x = ord[i];
      if (dis(x, p) > dis(x, q)) {
        if (dis(x, p) > dis(p, q)) q = x;
      } else {
        if (dis(x, q) > dis(p, q)) p = x;
      }
      g[i] = make_pair(p, q);
    }
    auto chk = [&] (int v, int x, long k) -> bool {
      if (v >= hi) return false;
      if (dis(x, g[v].first) > k) return false;
      if (dis(x, g[v].second) > k) return false;
      return true;
    };
    auto query = [&] (int x, long k) -> int {
      if (!chk(0, x, k)) return 0;
      auto l(0), r(hi - 1);
      while (l < r) {
        auto mid = (l + r + 1) / 2;
        if (chk(mid, x, k)) l = mid;
        else r = mid - 1;
      }
      return l + 1;
    };
    assert(hi);
    for (int i = 0; i < m; ++i) {
      int x; long k;
      cin >> x >> k;
      cout << query(--x, k) << '\n';
    }
  }
}

int main() { lyre::main(); }