#include <bits/stdc++.h>
using namespace std;
static constexpr int Maxn = 5e5 + 5, LogN = 19;
int n, qn, na, a[Maxn], ia[Maxn];
vector<tuple<int, int64_t>> g[Maxn];
int par[Maxn], dep[Maxn];
int edfn[Maxn], edn, iedfn[Maxn * 2];
int64_t wdep[Maxn];
void dfs(int u, int fa, int depth, int64_t wdepth) {
  par[u] = fa, dep[u] = depth, wdep[u] = wdepth;
  edfn[u] = ++edn, iedfn[edn] = u;
  for (const auto &[v, w]: g[u]) if (v != fa)
    dfs(v, u, depth + 1, wdepth + w), iedfn[++edn] = u;
} // dfs
int spt[LogN + 1][Maxn * 2], lowbit[Maxn * 2];
int min_dep(int x, int y) { return dep[iedfn[x]] < dep[iedfn[y]] ? x : y; }
int lca(int x, int y) {
  if (x == y) return x;
  x = edfn[x], y = edfn[y];
  if (x > y) swap(x, y);
  int k = lowbit[y - x + 1];
  return iedfn[min_dep(spt[k][x], spt[k][y - (1 << k) + 1])];
} // lca
int64_t distance(int x, int y) {
  int z = lca(x, y);
  return wdep[x] + wdep[y] - 2 * wdep[z];
} // distance
struct diam {
  int x, y;
  diam() = default;
  diam(int x, int y) : x(x), y(y) { }
  friend bool operator < (const diam &lhs, const diam &rhs)
  { return distance(lhs.x, lhs.y) < distance(rhs.x, rhs.y); }
  friend bool operator > (const diam &lhs, const diam &rhs)
  { return distance(lhs.x, lhs.y) > distance(rhs.x, rhs.y); }
  friend diam operator + (const diam &lhs, const diam &rhs)
  { return max({lhs, rhs, diam(lhs.x, rhs.x), diam(lhs.x, rhs.y), diam(lhs.y, rhs.x), diam(lhs.y, rhs.y)}); }
} d[Maxn];
int main(void) {
  cin.tie(nullptr)->sync_with_stdio(false);
  cin >> n >> qn; memset(ia, -1, sizeof(ia));
  for (int i = 1; i <= n; ++i) cin >> a[i];
  for (int i = 1; i <= n; ++i) if (a[i] <= n) ia[a[i]] = i;
  for (na = 0; ia[na] != -1; ++na);
  for (int i = 1; i < n; ++i) {
    int u, v; int64_t w;
    cin >> u >> v >> w;
    g[u].push_back({v, w});
    g[v].push_back({u, w});
  }
  dfs(1, 0, 1, 0LL);
  for (int i = 2; i <= edn; ++i) lowbit[i] = lowbit[i >> 1] + 1;
  for (int i = 1; i <= edn; ++i) spt[0][i] = i;
  for (int j = 1; j < LogN; ++j)
    for (int i = 1; i + (1 << j) - 1 <= edn; ++i)
      spt[j][i] = min_dep(spt[j - 1][i], spt[j - 1][i + (1 << j - 1)]);
  for (int i = 0; i < na; ++i)
    d[i] = (i == 0 ? diam(ia[0], ia[0]) : d[i - 1] + diam(ia[i], ia[i]));
  for (int qi = 1; qi <= qn; ++qi) {
    int u; int64_t w;
    cin >> u >> w;
    auto check = [&](int x)->bool {
      int64_t w1 = distance(d[x].x, u);
      int64_t w2 = distance(d[x].y, u);
      return max(w1, w2) > w;
    }; // main::check
    int low = 0, high = na - 1, ans = na;
    while (low <= high) {
      int mid = (low + high) / 2;
      if (check(mid)) ans = mid, high = mid - 1;
      else low = mid + 1;
    }
    printf("%d\n", ans);
  }
  return 0;
} // main