#include <bits/stdc++.h>
#define fi first
#define se second
#define PB push_back
#define EB emplace_back
using namespace std;
typedef long long i64;
const int maxn = 500000;
int w[maxn + 5];
struct edge { int v, w; };
vector<edge> g[maxn + 5];
i64 dep[maxn + 5];
pair<i64, int> mn[maxn + 5][20];
int lg2[maxn + 5];
int dfn[maxn + 5], stamp;
void dfs(int u, int fa) {
	mn[dfn[u] = ++stamp][0] = {dep[u], fa};
	for (const auto &[v, w] : g[u])
		if (v != fa) {
			dep[v] = dep[u] + w;
			dfs(v, u);
		}
}
inline int lca(int u, int v) {
	if (u == v) return u;
	u = dfn[u], v = dfn[v];
	if (u > v) swap(u, v);
	int t = lg2[v - u++];
	return min(mn[u][t], mn[v - (1 << t) + 1][t]).se;
}
inline int dis(int u, int v) { return dep[u] + dep[v] - 2 * dep[lca(u, v)]; }
int id[maxn + 5];
int p0[maxn + 5], p1[maxn + 5];
int main() {
	int n, q;
	scanf("%d%d", &n, &q);
	for (int i = 1; i <= n; i++) {
		scanf("%d", &w[i]);
		if (w[i] < n) id[w[i]] = i;
	}
	for (int i = 1; i < n; i++) {
		int u, v, w;
		scanf("%d%d%d", &u, &v, &w);
		g[u].PB({v, w}), g[v].PB({u, w});
	}
	dfs(1, 0);
	for (int i = n; i; i--)
		for (int j = 1; i + (1 << j) - 1 <= n; j++) mn[i][j] = min(mn[i][j - 1], mn[i + (1 << (j - 1))][j - 1]);
	for (int i = 2; i <= n; i++) lg2[i] = lg2[i >> 1] + 1;
	int mx;
	for (int i = 0; i <= n; i++) {
		if (!id[i]) { mx = i; break; }
		if (!i) p0[i] = p1[i] = id[i];
		else {
			i64 lst = dis(p0[i - 1], p1[i - 1]), n0 = dis(p0[i - 1], id[i]), n1 = dis(p1[i - 1], id[i]);
			if (lst >= n0 && lst >= n1) p0[i] = p0[i - 1], p1[i] = p1[i - 1];
			else if (n0 >= lst && n0 >= n1) p0[i] = p0[i - 1], p1[i] = id[i];
			else p0[i] = id[i], p1[i] = p1[i - 1];
		}
	}
	for (int i = 1; i <= q; i++) {
		int u; i64 k;
		scanf("%d%lld", &u, &k);
		int l = 0, r = mx;
		while (l < r) {
			int mid = (l + r + 1) / 2;
			if (dis(u, p0[mid - 1]) > k || dis(u, p1[mid - 1]) > k) r = mid - 1;
			else l = mid;
		}
		printf("%d\n", l);
	}
}