#include <bits/stdc++.h>
using namespace std;
#define C const
#define OP operator
#define pb push_back
#define ft first
#define sd second
#define VD void
#define I int
#define LL long long
#define STR string
#define mi (l + (r - l) / 2)
#define BE(v) v.begin(), v.end()
#define TTT template<typename T = I>
using PII = pair<I, I>;
TTT using V = vector<T>;

#define FORX(v) for(auto& x : v)
#define FORV(v, i) for (I i = 0, _n = v.size(), x = _n ? v[0] : 0;i < _n;x = v[++i])
#define FOR(i, b, e)  for(auto i = b, _e = (decltype(i))e;i != _e; ++i)
#define FORR(i, b, e) for(auto i = b, _e = (decltype(i))e;i != _e; --i)
#define FUNC(T, f, ...) function<T(__VA_ARGS__)> f = [&](__VA_ARGS__)->T

TTT VD setmin(T& a, C T& b) { if (b < a)a = b; }
TTT VD setmax(T& a, C T& b) { if (a < b)a = b; }

struct LCA
{
	I n, d; V<V<PII>> a{ {} }; V<I> id;
	LCA(V<V<I>>& e, V<V<I>>& g, V<LL>& dep, I rt = 1) :id(e.size())
	{
		FUNC(VD, dfs, I p, I fa, I dp)
		{
			id[p] = a[0].size(), a[0].pb({ dp,p });
			FORV(e[p], i)if (x != fa)dep[x] = dep[p] + g[p][i], dfs(x, p, dp + 1), a[0].pb({ dp,p });
		};
		dfs(rt, -1, 0);
		n = a[0].size(); d = ilogb(n); a.resize(d + 1, V<PII>(n));
		FOR(k, 0, d)FOR(i, 0, n - (1 << k))a[k + 1][i] = min(a[k][i], a[k][i + (1 << k)]);
	}
	I OP()(I x, I y)
	{
		if (id[x] > id[y])swap(x, y);
		x = id[x], y = id[y] + 1; I k = ilogb(y - x);
		return min(a[k][x], a[k][y - (1 << k)]).sd;
	}
};

VD test()
{
	I n, q;cin >> n >> q;++n;
	V<I> p(n);
	V<V<I>> e(n), g(n);
	V<LL> dep(n);
	V<PII> pr(1);
	FOR(i, 1, n)
	{
		I w;cin >> w;
		if (w < n)p[w] = i;
	}
	FOR(i, 2, n)
	{
		I u, v, w; cin >> u >> v >> w;
		e[u].pb(v), g[u].pb(w);
		e[v].pb(u), g[v].pb(w);
	}
	LCA lca(e, g, dep);

	FUNC(VD, dm, I & u, I & v, I w, LL & d)
	{
		d = dep[u] + dep[v] - 2 * dep[lca(u, v)];
		LL du = dep[u] + dep[w] - 2 * dep[lca(u, w)];
		LL dv = dep[v] + dep[w] - 2 * dep[lca(v, w)];
		if (dv > du)swap(u, v), swap(du, dv);
		if (du > d)v = w, d = du;
	};

	FOR(i, 0, n)
	{
		if (p[i] == 0)break;
		if (i == 0) { pr.pb({ p[i],p[i] });continue; }
		pr.pb(pr.back());LL d;
		dm(pr.back().ft, pr.back().sd, p[i], d);
	}

	while (q--)
	{
		LL x, k;cin >> x >> k;
		I l = 0, r = n + 1;
		FUNC(I, check, I l)
		{
			if (l == 0)return 1;
			if(l>=pr.size())return 0;
			I u = pr[l].ft, v = pr[l].sd;
			LL d; dm(u, v, x, d);
			return d <= k;
		};
		while (l + 1 < r)(check(mi) ? l : r) = mi;
		cout << l << '\n';
	}
}

I main()
{
	ios::sync_with_stdio(0);
	cin.tie(0), cout.tie(0);
	if (fopen("test.in", "r"))
	{
		freopen("test.in", "r", stdin);
		freopen("test.out", "w", stdout);
	}
	I t = 1;
	// cin >> t;
	while (t--)test();
	return 0;
}