#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 5e5 + 5;
int siz[N], mx[N], tot, ans[N], a[N], vis[N], n, q, rt;
ll t[N << 2];
vector<pair<int, int> > G[N];
vector<pair<ll, int> > Q[N];
vector<int> rec;
int idx[N << 2];
void ins(int x, ll y) {
	int p = idx[x];
	rec.push_back(p);
	t[p] = y;
	for (p >>= 1; p; p >>= 1)
		t[p] = max(t[p << 1], t[p << 1 | 1]);
}
//void ins(int p, int l, int r, int x, ll y) {
//	if (l == r) {
//		t[p] = y;
//		rec.push_back(p);
//		return;
//	}
//	ll mid = l + r >> 1;
//	if (x <= mid) ins(p << 1, l, mid, x, y);
//	else ins(p << 1 | 1, mid + 1, r, x, y);
//	t[p] = max(t[p << 1], t[p << 1 | 1]);
//}
int ask(int p, int l, int r, ll d) {
	if (l == r) return l;
	int mid = l + r >> 1;
	if (t[p << 1] > d) return ask(p << 1, l, mid, d);
	else return ask(p << 1 | 1, mid + 1, r, d);
}
void get_rt(int u, int fa) {
	siz[u] = 1;
	mx[u] = 0;
	for (auto &e : G[u]) {
		int v = e.first;
		if (v == fa || vis[v]) continue;
		get_rt(v, u);
		siz[u] += siz[v];
		if (siz[v] > mx[u]) mx[u] = siz[v];
	}
	mx[u] = max(mx[u], tot - siz[u]);
	if (rt == 0 || mx[u] < mx[rt]) rt = u;
}

void get_ans(int u, int fa, ll d) {
	for (auto &q : Q[u])
		ans[q.second] = min(ans[q.second], ask(1, 0, n, q.first - d));
	for (auto &e : G[u]) {
		int v = e.first;
		if (vis[v] || v == fa) continue;
		get_ans(v, u, d + e.second);
	}
}

void travel(int u, int fa, long long d) {
	if (a[u] <= n)
		ins(a[u], d);
	for (auto &e : G[u]) {
		int v = e.first;
		if (v == fa || vis[v]) continue;
		travel(v, u, d + e.second);
	}
}

void dfs(int u) {
	vis[u] = 1;
	
	rec.clear();
	if (a[u] <= n)
		ins(a[u], 0);
	for (auto e : G[u]) {
		int v = e.first;
		if (vis[v]) continue;
		get_ans(v, u, e.second);	
		travel(v, u, e.second);
	}
	for (auto q : Q[u])
		ans[q.second] = min(ans[q.second], ask(1, 0, n, q.first));
	for (int x : rec) {
		int y = x;
		while (y) t[y] = 0, y >>= 1;
	}
	
	rec.clear();
	for (int i = G[u].size() - 1; i >= 0; --i) {
		auto &e = G[u][i];
		int v = e.first;
		if (vis[v]) continue;
		get_ans(v, u, e.second);		
		travel(v, u, e.second);
	}
	for (int x : rec) {
		int y = x;
		while (y) t[y] = 0, y >>= 1;
	}

	for (auto &e : G[u]) {
		int v = e.first;
		if (vis[v]) continue;
		rt = 0, tot = siz[v];
		get_rt(v, u);
		dfs(rt);
	}

}
void build(int p, int l, int r) {
	if (l == r) {
		idx[l] = p;
		return;
	}
	int mid = l + r >> 1;
	build(p << 1, l, mid);
	build(p << 1 | 1, mid + 1, r);
}
int main() {
//	freopen("r.in", "r", stdin);
//	freopen("r.out", "w", stdout);
	scanf("%d%d", &n, &q);
	for (int i = 1; i <= n; ++i)
		scanf("%d", &a[i]);
	for (int i = 1; i < n; ++i) {
		int u, v, w;
		scanf("%d%d%d", &u, &v, &w);
		G[u].push_back(make_pair(v, w));
		G[v].push_back(make_pair(u, w));
	}
	for (int i = 1; i <= q; ++i) {
		int x; ll k;
		scanf("%d%lld", &x, &k);
		Q[x].push_back(make_pair(k, i));
		ans[i] = 1e9;
	}
	build(1, 0, n);
	
	rt = 0, tot = n;
	get_rt(1, -1);
	dfs(rt);

	sort(a + 1, a + n + 1);
	int mex = 0;
	for (;; ++mex)
		if (a[mex + 1] != mex)
			break;
	
	for (int i = 1; i <= q; ++i)
		printf("%d\n", min(ans[i], mex));
	return 0;
}