#include <bits/stdc++.h>
using namespace std;
using ll = long long;
struct Node {
	int ls, rs, mn;
} t[10000005];
const int N = 5e5 + 5;
int siz[N], mx[N], tot, ans[N], seg_rt, a[N], vis[N], ncnt, n, q, rt;
vector<pair<int, int> > G[N];
vector<pair<ll, int> > Q[N];
void ins(int &p, ll l, ll r, ll x, int y) {
	if (p == 0) {
		p = ++ncnt;
		t[p].ls = t[p].rs = 0;
		t[p].mn = 1e9;
	}
	if (l == r) {
		t[p].mn = min(t[p].mn, y);
		return;
	}
	ll mid = l + r >> 1;
	if (x <= mid) ins(t[p].ls, l, mid, x, y);
	else ins(t[p].rs, mid + 1, r, x, y);
	t[p].mn = 1e9;
	if (t[p].ls) t[p].mn = min(t[p].mn, t[t[p].ls].mn);
	if (t[p].rs) t[p].mn = min(t[p].mn, t[t[p].rs].mn);
}
int ask(int p, ll l, ll r, ll x) {
	if (r <= x || p == 0) return 1e9;
	if (l > x) return t[p].mn;
	ll mid = l + r >> 1;
	return min(ask(t[p].ls, l, mid, x), ask(t[p].rs, mid + 1, r, x));
}
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(seg_rt, 0, 5e14, 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) {
	ins(seg_rt, 0, 5e14, d, a[u]);
	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;
	seg_rt = ncnt = 0;
	ins(seg_rt, 0, 5e14, 0, a[u]);
	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(seg_rt, 0, 5e14, q.first));
	

	seg_rt = ncnt = 0;
	ins(seg_rt, 0, 5e14, 0, a[u]);
	for (auto i = G[u].rbegin(); i != G[u].rend(); ++i) {
		auto e = *i;
		int v = e.first;
		if (vis[v]) continue;		
		get_ans(v, u, e.second);		
		travel(v, u, e.second);
	}

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

}
int main() {
	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;
	}
	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;
}